Excretion = the removal of metabolic waste from the body
Metabolic waste = consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
There are 2 substances that are produced in very large amounts
Carbon dioxide
Nitrogen containing compounds such as urea
Note EGESTION is when your body removes undigested food by the process of defecation EXCRETION is when your body removes metabolic waste which has entered your cells
04142023 4
Where are these substances excreted
Carbon dioxide is passed from the cells of respiring tissues into the bloodstream It is transported in the blood (mostly in the form of hydrogencarbonate ions) to the lungs In the lungs the carbon dioxide diffuses into the alveoli to be excreted as we breathe
Urea is made from the break down of excess amino acids in the liver This process is called deamination Urea is passed into the bloodstream to be transported to the kidneys
it is transported in solution (dissolved in plasma)
In the kidneys urea is removed from the blood to become a part of urine
Urine is stored in the bladder before being excreted via the urethra
04142023 5
Why must these substances be removePart I
Carbon dioxide
Excess carbon dioxide can lead to toxicity via three main effects
1 Carbon dioxide is transported in the blood as hydrogencarbonate ions This occurs inside the red blood cells under the influence of carbonic anhydrase
H2CO3 H+ + HCO3-
The hydrogen ions combine with haemoglobin They compete with oxygen for space on the haemoglobin If there is too much carbon dioxide in the blood it will reduce oxygen transport
2 Carbon dioxide when bound to haem forms carbaminohaemoglobin (Carbon dioxide has a higher affinity for haem when the compound is formed carbaminohaemoglobin will have a lower affinity for oxygen than normal haem) Therefore it becomes difficult for oxygen to attach onto haem as carbon dioxide is strongly associated with haem
04142023 6
Why must these substances be removed
Part II3 Excess carbon dioxide can cause respiratory acidosis The carbon dioxide
dissolves in the blood plasma Once dissolved it can combine with water to produce carbonic acid
CO2 + H2O H2CO3
The carbonic acid dissociates to release hydrogen ions
H2CO3 H+ + HCO3-
The hydrogen ions lower the pH acidity within the blood circulation Proteins in the blood act as buffers to resist the change in pH
If the pH change is small the extra H+ ions are detected by the respiratory centre in the medulla oblongata of the brain resulting in
If the pH drops below 73 it results in slowed or difficult breathing headache
drowsiness restlessness tremor and confusion
May also be a rapid heart rate and changes in blood pressure
THIS IS RESPIRATORY ACIDOSIS (A MEDICAL EMERGENCY NEEDS TREATMENT IMMEDIATELY)
Respiratory acidosis can also be caused by diseases or conditions that affect the lungs themselves due to blockage of airway leading to increase in carbon dioxide These diseases include emphysema chronic bronchitis asthma or severe pneumonia Conditions such as swelling a foreign object or vomit in the airways are also causative
04142023 8
Why must these substances be removed
Part IV Nitrogenous Compounds
The body cannot store proteins or amino acids(aa) However aa contain as much energy as carbohydrates therefore we do not want to waste this energy source AA are transported to the liver and the potentially toxic amino group is removed (deamination)
Step 1 -The amino group initially forms a very soluble and highly toxic compound = ammonia
Amino acid + oxygen keto acid + ammonia
Step 2 - Ammonia is converted to a less soluble and less toxic compound = urea
Urea is then transported to the kidneys for excretion The remaining keto acid can be used directly in respiration to release its energy or it may be converted to a carbohydrate or fat for storage
04142023 9
122 The Liver
04142023 10
The structure of the liver
The liver cells namely the hepatocytes carry hundreds of metabolic processes and has an important role in homeostasis Therefore it is essential for a continuous supply of blood The internal structure of the liver is arranged to ensure that as much blood flows past as many liver cells as possible
04142023 11
Blood flow to the liver
TO
The liver has two blood supplies
Oxygenated blood from the heart Blood travels from the aorta via the HEPATIC ARTERY INTO THE LIVER
This supplies the oxygen essential for aerobic respiratory Hepatocytes are very active and require energy in the form of ATP so it is essential there is a good oxygen supply
Deoxygenated blood from the digestive system This enters the liver via the HEPATIC PORTAL VEIN This blood is rich in the products of digestion The concentration of the various compounds will be uncontrolled and the blood may contain toxic compounds that have been absorbed by the intestine
04142023 12
Blood flow from the liver
FROM Blood leaves the liver via the
HEPATIC VEIN This re-joins the vena cava and the blood returns to normal circulation
A Fourth vessel connected to the liver is not a blood vessel It is the bile duct Bile is a secretion from the liver It has both a digestive function and an excretory function The bile duct carries bile from the LIVER TO THE GALLBLADDER where it is stored until required to aid the digestion of fats in the small intestine
04142023 13
The arrangement of cells inside the liver
The liver is divided into lobes and further divided into cylindrical lobules
As the hepatic artery and hepatic portal vein enter the liver they split into smaller and smaller vessels which run parallel or between the lobules and are known as inter-lobular vessels
The blood from two blood vessels are mixed and passed through a special chamber called sinusoid which furthermore empty into the intra-lobular vessels a branch of the hepatic vein
The branches of the hepatic vein from different lobules join together to form the hepatic vein draining blood from the liver
As blood moves along the sinusoid it is in very close contact with the liver cells They are able to remove molecules from the blood and pass molecules into the blood
One of the many functions of the liver cells is to manufacture bile This is released into the bile canaliculi (small canals) These join together to form the bile duct which transports the bile to the gall bladder
04142023 14
Liver Cells
Hepatocytes are unspecialised simple cuboidal shaped cells which have many microvilli on their surface
They are however involved in many metabolic functions including
Protein synthesis
Transformation
Storage of carbohydrates
Synthesis of cholesterol and bile salts
Detoxification and other processes
This means that their cytoplasm must be very dense and is specialised in the amounts of certain organelles that it contains
04142023 15
Kupffer cells
Kupffer cells are specialised macrophages moving about in the sinusoids involved in the breakdown and recycling of red blood cells A product it produces during breakdown is bilirubin which is excreted as part of the bile and in faces Bilirubin is the brown pigment is faeces
Application Scenario
A common condition in newborns jaundice refers to the yellow color of the skin and whites of the eyes caused by excess bilirubin in the blood
It is also seen in adults where an excess chronic consumption of alcohol can have damaging effects on your liver meaning that you are not removing bilirubin from your liver and bile ducts quickly enough as it builds up in the blood it is deposited in the skinhellip The resulting is jaundice
Daily requirement is 40-60g of protein but daily consumption is far more greater therefore breakdown of amino acids are needed as accumulation leads to toxicity
Two step process occurs in the liver before the amino acid component is excreted DEAMINATION
ORNITHINE CYCLE
04142023 19
Formation of Urea DEAMINATION
Removal of NH3 group fro the amino acid with oxygen forming a keto acid (-RCOCOOH) and Ammonia (NH3)
Ammonia is highly toxic and very soluble therefore should not be allowed to accumulate in the blood circulation
On removal of NH3 group energy is released
THE ORNITHINE CYCLE
Ammonia is converted into a less soluble and less toxic substance when combined with CO2 forming Urea
Urea is further passed into the blood circulation and into the kidneys where it is filtered out of the blood circulation and is concentrated in the urine
04142023 20
Detoxification
The liver detoxifies alcohol and drugs Toxins can also be rendered harmless by oxidation reduction methylation or a combination with another molecule
Liver cells contain many enzymes that enable rendering of toxic molecules less toxic form
This includes catalase which converts H2O2 to oxygen and water
DETOXIFICATION OF ALCOHOL
Alcohol is a CNS depressant contains a lot of energy that can be used for respiration STEP 1 Ethanol Ethanol dehydrogenase Ethanal (occurs in the hepatocytes)
The hydrogens release in the steps above are combined with NAD NADH
NAD is required to oxidise and breakdown fatty acids for use in respiration
04142023 21
Future Possible Complications
If the liver has to detoxify too much alcohol it has insufficient NAD to deal with the fatty acids
These fatty acids are converted back to lipids and are stored in the hepatocytes causing the liver to become enlarged
Causes a condition known as fatty liver alcohol-related hepatitis or cirrhosis
04142023 22
Stretching Your KnowledgeScenario
Liver cells contain a large group of enzymes called the cytochrome P450 enzymes These are responsible for the breakdown of some toxic molecules such as cocaine and other drugs (recreational and medicinal) The P450s are most concentrated in the endoplasmic reticulum of liver cells As a result of variation these enzymes can be more effective in some people than in others (Caucasian population compared to Afro-Caribean population)
Many drugs can be more effective in some people than in others and may also cause variable side effects
Task
1 Suggest why the P450s are most concentrated in the endoplasmic reticulum
2 Suggest why many medicinal drugs have different side effects in different people
3 Explain why the P450s are not identical in every person
The P450s are proteins these are manufactured by the ribosomes that are attached to the endoplasmic reticulum ndash they can be packaged in vesicles and transported to where they are needed
Each person may have slightly different enzymes (evolution) These may break the drugs down in a slightly different way producing different by-products (SEs)
Genetic variation means that different people will have different alleles ndash these will produce slightly different enzymes
04142023 23
Questions
1 Why must ammonia be converted to urea
2 Explain why excess amino acids and alcohol should not be excreted
3 Suggest why the liver cells have large number of mitochondria and ribosomes
Ammonia is highly soluble and very toxic urea is less soluble and less toxic
They contain valuable energy that can be converted to useable forms Some amino acids can be converted into other amino acids
The mitochondria provide ATP (metabolic energy) for the active or energy-requiring processes eg protein synthesis mitosis active transport endo and exocytosis The ribosomes manufacture the many enzymes that are needed in liver cells
04142023 24
124 The Kidney
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 2
121 Excretion
04142023 3
What is excretion
Excretion = the removal of metabolic waste from the body
Metabolic waste = consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
There are 2 substances that are produced in very large amounts
Carbon dioxide
Nitrogen containing compounds such as urea
Note EGESTION is when your body removes undigested food by the process of defecation EXCRETION is when your body removes metabolic waste which has entered your cells
04142023 4
Where are these substances excreted
Carbon dioxide is passed from the cells of respiring tissues into the bloodstream It is transported in the blood (mostly in the form of hydrogencarbonate ions) to the lungs In the lungs the carbon dioxide diffuses into the alveoli to be excreted as we breathe
Urea is made from the break down of excess amino acids in the liver This process is called deamination Urea is passed into the bloodstream to be transported to the kidneys
it is transported in solution (dissolved in plasma)
In the kidneys urea is removed from the blood to become a part of urine
Urine is stored in the bladder before being excreted via the urethra
04142023 5
Why must these substances be removePart I
Carbon dioxide
Excess carbon dioxide can lead to toxicity via three main effects
1 Carbon dioxide is transported in the blood as hydrogencarbonate ions This occurs inside the red blood cells under the influence of carbonic anhydrase
H2CO3 H+ + HCO3-
The hydrogen ions combine with haemoglobin They compete with oxygen for space on the haemoglobin If there is too much carbon dioxide in the blood it will reduce oxygen transport
2 Carbon dioxide when bound to haem forms carbaminohaemoglobin (Carbon dioxide has a higher affinity for haem when the compound is formed carbaminohaemoglobin will have a lower affinity for oxygen than normal haem) Therefore it becomes difficult for oxygen to attach onto haem as carbon dioxide is strongly associated with haem
04142023 6
Why must these substances be removed
Part II3 Excess carbon dioxide can cause respiratory acidosis The carbon dioxide
dissolves in the blood plasma Once dissolved it can combine with water to produce carbonic acid
CO2 + H2O H2CO3
The carbonic acid dissociates to release hydrogen ions
H2CO3 H+ + HCO3-
The hydrogen ions lower the pH acidity within the blood circulation Proteins in the blood act as buffers to resist the change in pH
If the pH change is small the extra H+ ions are detected by the respiratory centre in the medulla oblongata of the brain resulting in
If the pH drops below 73 it results in slowed or difficult breathing headache
drowsiness restlessness tremor and confusion
May also be a rapid heart rate and changes in blood pressure
THIS IS RESPIRATORY ACIDOSIS (A MEDICAL EMERGENCY NEEDS TREATMENT IMMEDIATELY)
Respiratory acidosis can also be caused by diseases or conditions that affect the lungs themselves due to blockage of airway leading to increase in carbon dioxide These diseases include emphysema chronic bronchitis asthma or severe pneumonia Conditions such as swelling a foreign object or vomit in the airways are also causative
04142023 8
Why must these substances be removed
Part IV Nitrogenous Compounds
The body cannot store proteins or amino acids(aa) However aa contain as much energy as carbohydrates therefore we do not want to waste this energy source AA are transported to the liver and the potentially toxic amino group is removed (deamination)
Step 1 -The amino group initially forms a very soluble and highly toxic compound = ammonia
Amino acid + oxygen keto acid + ammonia
Step 2 - Ammonia is converted to a less soluble and less toxic compound = urea
Urea is then transported to the kidneys for excretion The remaining keto acid can be used directly in respiration to release its energy or it may be converted to a carbohydrate or fat for storage
04142023 9
122 The Liver
04142023 10
The structure of the liver
The liver cells namely the hepatocytes carry hundreds of metabolic processes and has an important role in homeostasis Therefore it is essential for a continuous supply of blood The internal structure of the liver is arranged to ensure that as much blood flows past as many liver cells as possible
04142023 11
Blood flow to the liver
TO
The liver has two blood supplies
Oxygenated blood from the heart Blood travels from the aorta via the HEPATIC ARTERY INTO THE LIVER
This supplies the oxygen essential for aerobic respiratory Hepatocytes are very active and require energy in the form of ATP so it is essential there is a good oxygen supply
Deoxygenated blood from the digestive system This enters the liver via the HEPATIC PORTAL VEIN This blood is rich in the products of digestion The concentration of the various compounds will be uncontrolled and the blood may contain toxic compounds that have been absorbed by the intestine
04142023 12
Blood flow from the liver
FROM Blood leaves the liver via the
HEPATIC VEIN This re-joins the vena cava and the blood returns to normal circulation
A Fourth vessel connected to the liver is not a blood vessel It is the bile duct Bile is a secretion from the liver It has both a digestive function and an excretory function The bile duct carries bile from the LIVER TO THE GALLBLADDER where it is stored until required to aid the digestion of fats in the small intestine
04142023 13
The arrangement of cells inside the liver
The liver is divided into lobes and further divided into cylindrical lobules
As the hepatic artery and hepatic portal vein enter the liver they split into smaller and smaller vessels which run parallel or between the lobules and are known as inter-lobular vessels
The blood from two blood vessels are mixed and passed through a special chamber called sinusoid which furthermore empty into the intra-lobular vessels a branch of the hepatic vein
The branches of the hepatic vein from different lobules join together to form the hepatic vein draining blood from the liver
As blood moves along the sinusoid it is in very close contact with the liver cells They are able to remove molecules from the blood and pass molecules into the blood
One of the many functions of the liver cells is to manufacture bile This is released into the bile canaliculi (small canals) These join together to form the bile duct which transports the bile to the gall bladder
04142023 14
Liver Cells
Hepatocytes are unspecialised simple cuboidal shaped cells which have many microvilli on their surface
They are however involved in many metabolic functions including
Protein synthesis
Transformation
Storage of carbohydrates
Synthesis of cholesterol and bile salts
Detoxification and other processes
This means that their cytoplasm must be very dense and is specialised in the amounts of certain organelles that it contains
04142023 15
Kupffer cells
Kupffer cells are specialised macrophages moving about in the sinusoids involved in the breakdown and recycling of red blood cells A product it produces during breakdown is bilirubin which is excreted as part of the bile and in faces Bilirubin is the brown pigment is faeces
Application Scenario
A common condition in newborns jaundice refers to the yellow color of the skin and whites of the eyes caused by excess bilirubin in the blood
It is also seen in adults where an excess chronic consumption of alcohol can have damaging effects on your liver meaning that you are not removing bilirubin from your liver and bile ducts quickly enough as it builds up in the blood it is deposited in the skinhellip The resulting is jaundice
Daily requirement is 40-60g of protein but daily consumption is far more greater therefore breakdown of amino acids are needed as accumulation leads to toxicity
Two step process occurs in the liver before the amino acid component is excreted DEAMINATION
ORNITHINE CYCLE
04142023 19
Formation of Urea DEAMINATION
Removal of NH3 group fro the amino acid with oxygen forming a keto acid (-RCOCOOH) and Ammonia (NH3)
Ammonia is highly toxic and very soluble therefore should not be allowed to accumulate in the blood circulation
On removal of NH3 group energy is released
THE ORNITHINE CYCLE
Ammonia is converted into a less soluble and less toxic substance when combined with CO2 forming Urea
Urea is further passed into the blood circulation and into the kidneys where it is filtered out of the blood circulation and is concentrated in the urine
04142023 20
Detoxification
The liver detoxifies alcohol and drugs Toxins can also be rendered harmless by oxidation reduction methylation or a combination with another molecule
Liver cells contain many enzymes that enable rendering of toxic molecules less toxic form
This includes catalase which converts H2O2 to oxygen and water
DETOXIFICATION OF ALCOHOL
Alcohol is a CNS depressant contains a lot of energy that can be used for respiration STEP 1 Ethanol Ethanol dehydrogenase Ethanal (occurs in the hepatocytes)
The hydrogens release in the steps above are combined with NAD NADH
NAD is required to oxidise and breakdown fatty acids for use in respiration
04142023 21
Future Possible Complications
If the liver has to detoxify too much alcohol it has insufficient NAD to deal with the fatty acids
These fatty acids are converted back to lipids and are stored in the hepatocytes causing the liver to become enlarged
Causes a condition known as fatty liver alcohol-related hepatitis or cirrhosis
04142023 22
Stretching Your KnowledgeScenario
Liver cells contain a large group of enzymes called the cytochrome P450 enzymes These are responsible for the breakdown of some toxic molecules such as cocaine and other drugs (recreational and medicinal) The P450s are most concentrated in the endoplasmic reticulum of liver cells As a result of variation these enzymes can be more effective in some people than in others (Caucasian population compared to Afro-Caribean population)
Many drugs can be more effective in some people than in others and may also cause variable side effects
Task
1 Suggest why the P450s are most concentrated in the endoplasmic reticulum
2 Suggest why many medicinal drugs have different side effects in different people
3 Explain why the P450s are not identical in every person
The P450s are proteins these are manufactured by the ribosomes that are attached to the endoplasmic reticulum ndash they can be packaged in vesicles and transported to where they are needed
Each person may have slightly different enzymes (evolution) These may break the drugs down in a slightly different way producing different by-products (SEs)
Genetic variation means that different people will have different alleles ndash these will produce slightly different enzymes
04142023 23
Questions
1 Why must ammonia be converted to urea
2 Explain why excess amino acids and alcohol should not be excreted
3 Suggest why the liver cells have large number of mitochondria and ribosomes
Ammonia is highly soluble and very toxic urea is less soluble and less toxic
They contain valuable energy that can be converted to useable forms Some amino acids can be converted into other amino acids
The mitochondria provide ATP (metabolic energy) for the active or energy-requiring processes eg protein synthesis mitosis active transport endo and exocytosis The ribosomes manufacture the many enzymes that are needed in liver cells
04142023 24
124 The Kidney
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 3
What is excretion
Excretion = the removal of metabolic waste from the body
Metabolic waste = consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
There are 2 substances that are produced in very large amounts
Carbon dioxide
Nitrogen containing compounds such as urea
Note EGESTION is when your body removes undigested food by the process of defecation EXCRETION is when your body removes metabolic waste which has entered your cells
04142023 4
Where are these substances excreted
Carbon dioxide is passed from the cells of respiring tissues into the bloodstream It is transported in the blood (mostly in the form of hydrogencarbonate ions) to the lungs In the lungs the carbon dioxide diffuses into the alveoli to be excreted as we breathe
Urea is made from the break down of excess amino acids in the liver This process is called deamination Urea is passed into the bloodstream to be transported to the kidneys
it is transported in solution (dissolved in plasma)
In the kidneys urea is removed from the blood to become a part of urine
Urine is stored in the bladder before being excreted via the urethra
04142023 5
Why must these substances be removePart I
Carbon dioxide
Excess carbon dioxide can lead to toxicity via three main effects
1 Carbon dioxide is transported in the blood as hydrogencarbonate ions This occurs inside the red blood cells under the influence of carbonic anhydrase
H2CO3 H+ + HCO3-
The hydrogen ions combine with haemoglobin They compete with oxygen for space on the haemoglobin If there is too much carbon dioxide in the blood it will reduce oxygen transport
2 Carbon dioxide when bound to haem forms carbaminohaemoglobin (Carbon dioxide has a higher affinity for haem when the compound is formed carbaminohaemoglobin will have a lower affinity for oxygen than normal haem) Therefore it becomes difficult for oxygen to attach onto haem as carbon dioxide is strongly associated with haem
04142023 6
Why must these substances be removed
Part II3 Excess carbon dioxide can cause respiratory acidosis The carbon dioxide
dissolves in the blood plasma Once dissolved it can combine with water to produce carbonic acid
CO2 + H2O H2CO3
The carbonic acid dissociates to release hydrogen ions
H2CO3 H+ + HCO3-
The hydrogen ions lower the pH acidity within the blood circulation Proteins in the blood act as buffers to resist the change in pH
If the pH change is small the extra H+ ions are detected by the respiratory centre in the medulla oblongata of the brain resulting in
If the pH drops below 73 it results in slowed or difficult breathing headache
drowsiness restlessness tremor and confusion
May also be a rapid heart rate and changes in blood pressure
THIS IS RESPIRATORY ACIDOSIS (A MEDICAL EMERGENCY NEEDS TREATMENT IMMEDIATELY)
Respiratory acidosis can also be caused by diseases or conditions that affect the lungs themselves due to blockage of airway leading to increase in carbon dioxide These diseases include emphysema chronic bronchitis asthma or severe pneumonia Conditions such as swelling a foreign object or vomit in the airways are also causative
04142023 8
Why must these substances be removed
Part IV Nitrogenous Compounds
The body cannot store proteins or amino acids(aa) However aa contain as much energy as carbohydrates therefore we do not want to waste this energy source AA are transported to the liver and the potentially toxic amino group is removed (deamination)
Step 1 -The amino group initially forms a very soluble and highly toxic compound = ammonia
Amino acid + oxygen keto acid + ammonia
Step 2 - Ammonia is converted to a less soluble and less toxic compound = urea
Urea is then transported to the kidneys for excretion The remaining keto acid can be used directly in respiration to release its energy or it may be converted to a carbohydrate or fat for storage
04142023 9
122 The Liver
04142023 10
The structure of the liver
The liver cells namely the hepatocytes carry hundreds of metabolic processes and has an important role in homeostasis Therefore it is essential for a continuous supply of blood The internal structure of the liver is arranged to ensure that as much blood flows past as many liver cells as possible
04142023 11
Blood flow to the liver
TO
The liver has two blood supplies
Oxygenated blood from the heart Blood travels from the aorta via the HEPATIC ARTERY INTO THE LIVER
This supplies the oxygen essential for aerobic respiratory Hepatocytes are very active and require energy in the form of ATP so it is essential there is a good oxygen supply
Deoxygenated blood from the digestive system This enters the liver via the HEPATIC PORTAL VEIN This blood is rich in the products of digestion The concentration of the various compounds will be uncontrolled and the blood may contain toxic compounds that have been absorbed by the intestine
04142023 12
Blood flow from the liver
FROM Blood leaves the liver via the
HEPATIC VEIN This re-joins the vena cava and the blood returns to normal circulation
A Fourth vessel connected to the liver is not a blood vessel It is the bile duct Bile is a secretion from the liver It has both a digestive function and an excretory function The bile duct carries bile from the LIVER TO THE GALLBLADDER where it is stored until required to aid the digestion of fats in the small intestine
04142023 13
The arrangement of cells inside the liver
The liver is divided into lobes and further divided into cylindrical lobules
As the hepatic artery and hepatic portal vein enter the liver they split into smaller and smaller vessels which run parallel or between the lobules and are known as inter-lobular vessels
The blood from two blood vessels are mixed and passed through a special chamber called sinusoid which furthermore empty into the intra-lobular vessels a branch of the hepatic vein
The branches of the hepatic vein from different lobules join together to form the hepatic vein draining blood from the liver
As blood moves along the sinusoid it is in very close contact with the liver cells They are able to remove molecules from the blood and pass molecules into the blood
One of the many functions of the liver cells is to manufacture bile This is released into the bile canaliculi (small canals) These join together to form the bile duct which transports the bile to the gall bladder
04142023 14
Liver Cells
Hepatocytes are unspecialised simple cuboidal shaped cells which have many microvilli on their surface
They are however involved in many metabolic functions including
Protein synthesis
Transformation
Storage of carbohydrates
Synthesis of cholesterol and bile salts
Detoxification and other processes
This means that their cytoplasm must be very dense and is specialised in the amounts of certain organelles that it contains
04142023 15
Kupffer cells
Kupffer cells are specialised macrophages moving about in the sinusoids involved in the breakdown and recycling of red blood cells A product it produces during breakdown is bilirubin which is excreted as part of the bile and in faces Bilirubin is the brown pigment is faeces
Application Scenario
A common condition in newborns jaundice refers to the yellow color of the skin and whites of the eyes caused by excess bilirubin in the blood
It is also seen in adults where an excess chronic consumption of alcohol can have damaging effects on your liver meaning that you are not removing bilirubin from your liver and bile ducts quickly enough as it builds up in the blood it is deposited in the skinhellip The resulting is jaundice
Daily requirement is 40-60g of protein but daily consumption is far more greater therefore breakdown of amino acids are needed as accumulation leads to toxicity
Two step process occurs in the liver before the amino acid component is excreted DEAMINATION
ORNITHINE CYCLE
04142023 19
Formation of Urea DEAMINATION
Removal of NH3 group fro the amino acid with oxygen forming a keto acid (-RCOCOOH) and Ammonia (NH3)
Ammonia is highly toxic and very soluble therefore should not be allowed to accumulate in the blood circulation
On removal of NH3 group energy is released
THE ORNITHINE CYCLE
Ammonia is converted into a less soluble and less toxic substance when combined with CO2 forming Urea
Urea is further passed into the blood circulation and into the kidneys where it is filtered out of the blood circulation and is concentrated in the urine
04142023 20
Detoxification
The liver detoxifies alcohol and drugs Toxins can also be rendered harmless by oxidation reduction methylation or a combination with another molecule
Liver cells contain many enzymes that enable rendering of toxic molecules less toxic form
This includes catalase which converts H2O2 to oxygen and water
DETOXIFICATION OF ALCOHOL
Alcohol is a CNS depressant contains a lot of energy that can be used for respiration STEP 1 Ethanol Ethanol dehydrogenase Ethanal (occurs in the hepatocytes)
The hydrogens release in the steps above are combined with NAD NADH
NAD is required to oxidise and breakdown fatty acids for use in respiration
04142023 21
Future Possible Complications
If the liver has to detoxify too much alcohol it has insufficient NAD to deal with the fatty acids
These fatty acids are converted back to lipids and are stored in the hepatocytes causing the liver to become enlarged
Causes a condition known as fatty liver alcohol-related hepatitis or cirrhosis
04142023 22
Stretching Your KnowledgeScenario
Liver cells contain a large group of enzymes called the cytochrome P450 enzymes These are responsible for the breakdown of some toxic molecules such as cocaine and other drugs (recreational and medicinal) The P450s are most concentrated in the endoplasmic reticulum of liver cells As a result of variation these enzymes can be more effective in some people than in others (Caucasian population compared to Afro-Caribean population)
Many drugs can be more effective in some people than in others and may also cause variable side effects
Task
1 Suggest why the P450s are most concentrated in the endoplasmic reticulum
2 Suggest why many medicinal drugs have different side effects in different people
3 Explain why the P450s are not identical in every person
The P450s are proteins these are manufactured by the ribosomes that are attached to the endoplasmic reticulum ndash they can be packaged in vesicles and transported to where they are needed
Each person may have slightly different enzymes (evolution) These may break the drugs down in a slightly different way producing different by-products (SEs)
Genetic variation means that different people will have different alleles ndash these will produce slightly different enzymes
04142023 23
Questions
1 Why must ammonia be converted to urea
2 Explain why excess amino acids and alcohol should not be excreted
3 Suggest why the liver cells have large number of mitochondria and ribosomes
Ammonia is highly soluble and very toxic urea is less soluble and less toxic
They contain valuable energy that can be converted to useable forms Some amino acids can be converted into other amino acids
The mitochondria provide ATP (metabolic energy) for the active or energy-requiring processes eg protein synthesis mitosis active transport endo and exocytosis The ribosomes manufacture the many enzymes that are needed in liver cells
04142023 24
124 The Kidney
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 4
Where are these substances excreted
Carbon dioxide is passed from the cells of respiring tissues into the bloodstream It is transported in the blood (mostly in the form of hydrogencarbonate ions) to the lungs In the lungs the carbon dioxide diffuses into the alveoli to be excreted as we breathe
Urea is made from the break down of excess amino acids in the liver This process is called deamination Urea is passed into the bloodstream to be transported to the kidneys
it is transported in solution (dissolved in plasma)
In the kidneys urea is removed from the blood to become a part of urine
Urine is stored in the bladder before being excreted via the urethra
04142023 5
Why must these substances be removePart I
Carbon dioxide
Excess carbon dioxide can lead to toxicity via three main effects
1 Carbon dioxide is transported in the blood as hydrogencarbonate ions This occurs inside the red blood cells under the influence of carbonic anhydrase
H2CO3 H+ + HCO3-
The hydrogen ions combine with haemoglobin They compete with oxygen for space on the haemoglobin If there is too much carbon dioxide in the blood it will reduce oxygen transport
2 Carbon dioxide when bound to haem forms carbaminohaemoglobin (Carbon dioxide has a higher affinity for haem when the compound is formed carbaminohaemoglobin will have a lower affinity for oxygen than normal haem) Therefore it becomes difficult for oxygen to attach onto haem as carbon dioxide is strongly associated with haem
04142023 6
Why must these substances be removed
Part II3 Excess carbon dioxide can cause respiratory acidosis The carbon dioxide
dissolves in the blood plasma Once dissolved it can combine with water to produce carbonic acid
CO2 + H2O H2CO3
The carbonic acid dissociates to release hydrogen ions
H2CO3 H+ + HCO3-
The hydrogen ions lower the pH acidity within the blood circulation Proteins in the blood act as buffers to resist the change in pH
If the pH change is small the extra H+ ions are detected by the respiratory centre in the medulla oblongata of the brain resulting in
If the pH drops below 73 it results in slowed or difficult breathing headache
drowsiness restlessness tremor and confusion
May also be a rapid heart rate and changes in blood pressure
THIS IS RESPIRATORY ACIDOSIS (A MEDICAL EMERGENCY NEEDS TREATMENT IMMEDIATELY)
Respiratory acidosis can also be caused by diseases or conditions that affect the lungs themselves due to blockage of airway leading to increase in carbon dioxide These diseases include emphysema chronic bronchitis asthma or severe pneumonia Conditions such as swelling a foreign object or vomit in the airways are also causative
04142023 8
Why must these substances be removed
Part IV Nitrogenous Compounds
The body cannot store proteins or amino acids(aa) However aa contain as much energy as carbohydrates therefore we do not want to waste this energy source AA are transported to the liver and the potentially toxic amino group is removed (deamination)
Step 1 -The amino group initially forms a very soluble and highly toxic compound = ammonia
Amino acid + oxygen keto acid + ammonia
Step 2 - Ammonia is converted to a less soluble and less toxic compound = urea
Urea is then transported to the kidneys for excretion The remaining keto acid can be used directly in respiration to release its energy or it may be converted to a carbohydrate or fat for storage
04142023 9
122 The Liver
04142023 10
The structure of the liver
The liver cells namely the hepatocytes carry hundreds of metabolic processes and has an important role in homeostasis Therefore it is essential for a continuous supply of blood The internal structure of the liver is arranged to ensure that as much blood flows past as many liver cells as possible
04142023 11
Blood flow to the liver
TO
The liver has two blood supplies
Oxygenated blood from the heart Blood travels from the aorta via the HEPATIC ARTERY INTO THE LIVER
This supplies the oxygen essential for aerobic respiratory Hepatocytes are very active and require energy in the form of ATP so it is essential there is a good oxygen supply
Deoxygenated blood from the digestive system This enters the liver via the HEPATIC PORTAL VEIN This blood is rich in the products of digestion The concentration of the various compounds will be uncontrolled and the blood may contain toxic compounds that have been absorbed by the intestine
04142023 12
Blood flow from the liver
FROM Blood leaves the liver via the
HEPATIC VEIN This re-joins the vena cava and the blood returns to normal circulation
A Fourth vessel connected to the liver is not a blood vessel It is the bile duct Bile is a secretion from the liver It has both a digestive function and an excretory function The bile duct carries bile from the LIVER TO THE GALLBLADDER where it is stored until required to aid the digestion of fats in the small intestine
04142023 13
The arrangement of cells inside the liver
The liver is divided into lobes and further divided into cylindrical lobules
As the hepatic artery and hepatic portal vein enter the liver they split into smaller and smaller vessels which run parallel or between the lobules and are known as inter-lobular vessels
The blood from two blood vessels are mixed and passed through a special chamber called sinusoid which furthermore empty into the intra-lobular vessels a branch of the hepatic vein
The branches of the hepatic vein from different lobules join together to form the hepatic vein draining blood from the liver
As blood moves along the sinusoid it is in very close contact with the liver cells They are able to remove molecules from the blood and pass molecules into the blood
One of the many functions of the liver cells is to manufacture bile This is released into the bile canaliculi (small canals) These join together to form the bile duct which transports the bile to the gall bladder
04142023 14
Liver Cells
Hepatocytes are unspecialised simple cuboidal shaped cells which have many microvilli on their surface
They are however involved in many metabolic functions including
Protein synthesis
Transformation
Storage of carbohydrates
Synthesis of cholesterol and bile salts
Detoxification and other processes
This means that their cytoplasm must be very dense and is specialised in the amounts of certain organelles that it contains
04142023 15
Kupffer cells
Kupffer cells are specialised macrophages moving about in the sinusoids involved in the breakdown and recycling of red blood cells A product it produces during breakdown is bilirubin which is excreted as part of the bile and in faces Bilirubin is the brown pigment is faeces
Application Scenario
A common condition in newborns jaundice refers to the yellow color of the skin and whites of the eyes caused by excess bilirubin in the blood
It is also seen in adults where an excess chronic consumption of alcohol can have damaging effects on your liver meaning that you are not removing bilirubin from your liver and bile ducts quickly enough as it builds up in the blood it is deposited in the skinhellip The resulting is jaundice
Daily requirement is 40-60g of protein but daily consumption is far more greater therefore breakdown of amino acids are needed as accumulation leads to toxicity
Two step process occurs in the liver before the amino acid component is excreted DEAMINATION
ORNITHINE CYCLE
04142023 19
Formation of Urea DEAMINATION
Removal of NH3 group fro the amino acid with oxygen forming a keto acid (-RCOCOOH) and Ammonia (NH3)
Ammonia is highly toxic and very soluble therefore should not be allowed to accumulate in the blood circulation
On removal of NH3 group energy is released
THE ORNITHINE CYCLE
Ammonia is converted into a less soluble and less toxic substance when combined with CO2 forming Urea
Urea is further passed into the blood circulation and into the kidneys where it is filtered out of the blood circulation and is concentrated in the urine
04142023 20
Detoxification
The liver detoxifies alcohol and drugs Toxins can also be rendered harmless by oxidation reduction methylation or a combination with another molecule
Liver cells contain many enzymes that enable rendering of toxic molecules less toxic form
This includes catalase which converts H2O2 to oxygen and water
DETOXIFICATION OF ALCOHOL
Alcohol is a CNS depressant contains a lot of energy that can be used for respiration STEP 1 Ethanol Ethanol dehydrogenase Ethanal (occurs in the hepatocytes)
The hydrogens release in the steps above are combined with NAD NADH
NAD is required to oxidise and breakdown fatty acids for use in respiration
04142023 21
Future Possible Complications
If the liver has to detoxify too much alcohol it has insufficient NAD to deal with the fatty acids
These fatty acids are converted back to lipids and are stored in the hepatocytes causing the liver to become enlarged
Causes a condition known as fatty liver alcohol-related hepatitis or cirrhosis
04142023 22
Stretching Your KnowledgeScenario
Liver cells contain a large group of enzymes called the cytochrome P450 enzymes These are responsible for the breakdown of some toxic molecules such as cocaine and other drugs (recreational and medicinal) The P450s are most concentrated in the endoplasmic reticulum of liver cells As a result of variation these enzymes can be more effective in some people than in others (Caucasian population compared to Afro-Caribean population)
Many drugs can be more effective in some people than in others and may also cause variable side effects
Task
1 Suggest why the P450s are most concentrated in the endoplasmic reticulum
2 Suggest why many medicinal drugs have different side effects in different people
3 Explain why the P450s are not identical in every person
The P450s are proteins these are manufactured by the ribosomes that are attached to the endoplasmic reticulum ndash they can be packaged in vesicles and transported to where they are needed
Each person may have slightly different enzymes (evolution) These may break the drugs down in a slightly different way producing different by-products (SEs)
Genetic variation means that different people will have different alleles ndash these will produce slightly different enzymes
04142023 23
Questions
1 Why must ammonia be converted to urea
2 Explain why excess amino acids and alcohol should not be excreted
3 Suggest why the liver cells have large number of mitochondria and ribosomes
Ammonia is highly soluble and very toxic urea is less soluble and less toxic
They contain valuable energy that can be converted to useable forms Some amino acids can be converted into other amino acids
The mitochondria provide ATP (metabolic energy) for the active or energy-requiring processes eg protein synthesis mitosis active transport endo and exocytosis The ribosomes manufacture the many enzymes that are needed in liver cells
04142023 24
124 The Kidney
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 5
Why must these substances be removePart I
Carbon dioxide
Excess carbon dioxide can lead to toxicity via three main effects
1 Carbon dioxide is transported in the blood as hydrogencarbonate ions This occurs inside the red blood cells under the influence of carbonic anhydrase
H2CO3 H+ + HCO3-
The hydrogen ions combine with haemoglobin They compete with oxygen for space on the haemoglobin If there is too much carbon dioxide in the blood it will reduce oxygen transport
2 Carbon dioxide when bound to haem forms carbaminohaemoglobin (Carbon dioxide has a higher affinity for haem when the compound is formed carbaminohaemoglobin will have a lower affinity for oxygen than normal haem) Therefore it becomes difficult for oxygen to attach onto haem as carbon dioxide is strongly associated with haem
04142023 6
Why must these substances be removed
Part II3 Excess carbon dioxide can cause respiratory acidosis The carbon dioxide
dissolves in the blood plasma Once dissolved it can combine with water to produce carbonic acid
CO2 + H2O H2CO3
The carbonic acid dissociates to release hydrogen ions
H2CO3 H+ + HCO3-
The hydrogen ions lower the pH acidity within the blood circulation Proteins in the blood act as buffers to resist the change in pH
If the pH change is small the extra H+ ions are detected by the respiratory centre in the medulla oblongata of the brain resulting in
If the pH drops below 73 it results in slowed or difficult breathing headache
drowsiness restlessness tremor and confusion
May also be a rapid heart rate and changes in blood pressure
THIS IS RESPIRATORY ACIDOSIS (A MEDICAL EMERGENCY NEEDS TREATMENT IMMEDIATELY)
Respiratory acidosis can also be caused by diseases or conditions that affect the lungs themselves due to blockage of airway leading to increase in carbon dioxide These diseases include emphysema chronic bronchitis asthma or severe pneumonia Conditions such as swelling a foreign object or vomit in the airways are also causative
04142023 8
Why must these substances be removed
Part IV Nitrogenous Compounds
The body cannot store proteins or amino acids(aa) However aa contain as much energy as carbohydrates therefore we do not want to waste this energy source AA are transported to the liver and the potentially toxic amino group is removed (deamination)
Step 1 -The amino group initially forms a very soluble and highly toxic compound = ammonia
Amino acid + oxygen keto acid + ammonia
Step 2 - Ammonia is converted to a less soluble and less toxic compound = urea
Urea is then transported to the kidneys for excretion The remaining keto acid can be used directly in respiration to release its energy or it may be converted to a carbohydrate or fat for storage
04142023 9
122 The Liver
04142023 10
The structure of the liver
The liver cells namely the hepatocytes carry hundreds of metabolic processes and has an important role in homeostasis Therefore it is essential for a continuous supply of blood The internal structure of the liver is arranged to ensure that as much blood flows past as many liver cells as possible
04142023 11
Blood flow to the liver
TO
The liver has two blood supplies
Oxygenated blood from the heart Blood travels from the aorta via the HEPATIC ARTERY INTO THE LIVER
This supplies the oxygen essential for aerobic respiratory Hepatocytes are very active and require energy in the form of ATP so it is essential there is a good oxygen supply
Deoxygenated blood from the digestive system This enters the liver via the HEPATIC PORTAL VEIN This blood is rich in the products of digestion The concentration of the various compounds will be uncontrolled and the blood may contain toxic compounds that have been absorbed by the intestine
04142023 12
Blood flow from the liver
FROM Blood leaves the liver via the
HEPATIC VEIN This re-joins the vena cava and the blood returns to normal circulation
A Fourth vessel connected to the liver is not a blood vessel It is the bile duct Bile is a secretion from the liver It has both a digestive function and an excretory function The bile duct carries bile from the LIVER TO THE GALLBLADDER where it is stored until required to aid the digestion of fats in the small intestine
04142023 13
The arrangement of cells inside the liver
The liver is divided into lobes and further divided into cylindrical lobules
As the hepatic artery and hepatic portal vein enter the liver they split into smaller and smaller vessels which run parallel or between the lobules and are known as inter-lobular vessels
The blood from two blood vessels are mixed and passed through a special chamber called sinusoid which furthermore empty into the intra-lobular vessels a branch of the hepatic vein
The branches of the hepatic vein from different lobules join together to form the hepatic vein draining blood from the liver
As blood moves along the sinusoid it is in very close contact with the liver cells They are able to remove molecules from the blood and pass molecules into the blood
One of the many functions of the liver cells is to manufacture bile This is released into the bile canaliculi (small canals) These join together to form the bile duct which transports the bile to the gall bladder
04142023 14
Liver Cells
Hepatocytes are unspecialised simple cuboidal shaped cells which have many microvilli on their surface
They are however involved in many metabolic functions including
Protein synthesis
Transformation
Storage of carbohydrates
Synthesis of cholesterol and bile salts
Detoxification and other processes
This means that their cytoplasm must be very dense and is specialised in the amounts of certain organelles that it contains
04142023 15
Kupffer cells
Kupffer cells are specialised macrophages moving about in the sinusoids involved in the breakdown and recycling of red blood cells A product it produces during breakdown is bilirubin which is excreted as part of the bile and in faces Bilirubin is the brown pigment is faeces
Application Scenario
A common condition in newborns jaundice refers to the yellow color of the skin and whites of the eyes caused by excess bilirubin in the blood
It is also seen in adults where an excess chronic consumption of alcohol can have damaging effects on your liver meaning that you are not removing bilirubin from your liver and bile ducts quickly enough as it builds up in the blood it is deposited in the skinhellip The resulting is jaundice
Daily requirement is 40-60g of protein but daily consumption is far more greater therefore breakdown of amino acids are needed as accumulation leads to toxicity
Two step process occurs in the liver before the amino acid component is excreted DEAMINATION
ORNITHINE CYCLE
04142023 19
Formation of Urea DEAMINATION
Removal of NH3 group fro the amino acid with oxygen forming a keto acid (-RCOCOOH) and Ammonia (NH3)
Ammonia is highly toxic and very soluble therefore should not be allowed to accumulate in the blood circulation
On removal of NH3 group energy is released
THE ORNITHINE CYCLE
Ammonia is converted into a less soluble and less toxic substance when combined with CO2 forming Urea
Urea is further passed into the blood circulation and into the kidneys where it is filtered out of the blood circulation and is concentrated in the urine
04142023 20
Detoxification
The liver detoxifies alcohol and drugs Toxins can also be rendered harmless by oxidation reduction methylation or a combination with another molecule
Liver cells contain many enzymes that enable rendering of toxic molecules less toxic form
This includes catalase which converts H2O2 to oxygen and water
DETOXIFICATION OF ALCOHOL
Alcohol is a CNS depressant contains a lot of energy that can be used for respiration STEP 1 Ethanol Ethanol dehydrogenase Ethanal (occurs in the hepatocytes)
The hydrogens release in the steps above are combined with NAD NADH
NAD is required to oxidise and breakdown fatty acids for use in respiration
04142023 21
Future Possible Complications
If the liver has to detoxify too much alcohol it has insufficient NAD to deal with the fatty acids
These fatty acids are converted back to lipids and are stored in the hepatocytes causing the liver to become enlarged
Causes a condition known as fatty liver alcohol-related hepatitis or cirrhosis
04142023 22
Stretching Your KnowledgeScenario
Liver cells contain a large group of enzymes called the cytochrome P450 enzymes These are responsible for the breakdown of some toxic molecules such as cocaine and other drugs (recreational and medicinal) The P450s are most concentrated in the endoplasmic reticulum of liver cells As a result of variation these enzymes can be more effective in some people than in others (Caucasian population compared to Afro-Caribean population)
Many drugs can be more effective in some people than in others and may also cause variable side effects
Task
1 Suggest why the P450s are most concentrated in the endoplasmic reticulum
2 Suggest why many medicinal drugs have different side effects in different people
3 Explain why the P450s are not identical in every person
The P450s are proteins these are manufactured by the ribosomes that are attached to the endoplasmic reticulum ndash they can be packaged in vesicles and transported to where they are needed
Each person may have slightly different enzymes (evolution) These may break the drugs down in a slightly different way producing different by-products (SEs)
Genetic variation means that different people will have different alleles ndash these will produce slightly different enzymes
04142023 23
Questions
1 Why must ammonia be converted to urea
2 Explain why excess amino acids and alcohol should not be excreted
3 Suggest why the liver cells have large number of mitochondria and ribosomes
Ammonia is highly soluble and very toxic urea is less soluble and less toxic
They contain valuable energy that can be converted to useable forms Some amino acids can be converted into other amino acids
The mitochondria provide ATP (metabolic energy) for the active or energy-requiring processes eg protein synthesis mitosis active transport endo and exocytosis The ribosomes manufacture the many enzymes that are needed in liver cells
04142023 24
124 The Kidney
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 6
Why must these substances be removed
Part II3 Excess carbon dioxide can cause respiratory acidosis The carbon dioxide
dissolves in the blood plasma Once dissolved it can combine with water to produce carbonic acid
CO2 + H2O H2CO3
The carbonic acid dissociates to release hydrogen ions
H2CO3 H+ + HCO3-
The hydrogen ions lower the pH acidity within the blood circulation Proteins in the blood act as buffers to resist the change in pH
If the pH change is small the extra H+ ions are detected by the respiratory centre in the medulla oblongata of the brain resulting in
If the pH drops below 73 it results in slowed or difficult breathing headache
drowsiness restlessness tremor and confusion
May also be a rapid heart rate and changes in blood pressure
THIS IS RESPIRATORY ACIDOSIS (A MEDICAL EMERGENCY NEEDS TREATMENT IMMEDIATELY)
Respiratory acidosis can also be caused by diseases or conditions that affect the lungs themselves due to blockage of airway leading to increase in carbon dioxide These diseases include emphysema chronic bronchitis asthma or severe pneumonia Conditions such as swelling a foreign object or vomit in the airways are also causative
04142023 8
Why must these substances be removed
Part IV Nitrogenous Compounds
The body cannot store proteins or amino acids(aa) However aa contain as much energy as carbohydrates therefore we do not want to waste this energy source AA are transported to the liver and the potentially toxic amino group is removed (deamination)
Step 1 -The amino group initially forms a very soluble and highly toxic compound = ammonia
Amino acid + oxygen keto acid + ammonia
Step 2 - Ammonia is converted to a less soluble and less toxic compound = urea
Urea is then transported to the kidneys for excretion The remaining keto acid can be used directly in respiration to release its energy or it may be converted to a carbohydrate or fat for storage
04142023 9
122 The Liver
04142023 10
The structure of the liver
The liver cells namely the hepatocytes carry hundreds of metabolic processes and has an important role in homeostasis Therefore it is essential for a continuous supply of blood The internal structure of the liver is arranged to ensure that as much blood flows past as many liver cells as possible
04142023 11
Blood flow to the liver
TO
The liver has two blood supplies
Oxygenated blood from the heart Blood travels from the aorta via the HEPATIC ARTERY INTO THE LIVER
This supplies the oxygen essential for aerobic respiratory Hepatocytes are very active and require energy in the form of ATP so it is essential there is a good oxygen supply
Deoxygenated blood from the digestive system This enters the liver via the HEPATIC PORTAL VEIN This blood is rich in the products of digestion The concentration of the various compounds will be uncontrolled and the blood may contain toxic compounds that have been absorbed by the intestine
04142023 12
Blood flow from the liver
FROM Blood leaves the liver via the
HEPATIC VEIN This re-joins the vena cava and the blood returns to normal circulation
A Fourth vessel connected to the liver is not a blood vessel It is the bile duct Bile is a secretion from the liver It has both a digestive function and an excretory function The bile duct carries bile from the LIVER TO THE GALLBLADDER where it is stored until required to aid the digestion of fats in the small intestine
04142023 13
The arrangement of cells inside the liver
The liver is divided into lobes and further divided into cylindrical lobules
As the hepatic artery and hepatic portal vein enter the liver they split into smaller and smaller vessels which run parallel or between the lobules and are known as inter-lobular vessels
The blood from two blood vessels are mixed and passed through a special chamber called sinusoid which furthermore empty into the intra-lobular vessels a branch of the hepatic vein
The branches of the hepatic vein from different lobules join together to form the hepatic vein draining blood from the liver
As blood moves along the sinusoid it is in very close contact with the liver cells They are able to remove molecules from the blood and pass molecules into the blood
One of the many functions of the liver cells is to manufacture bile This is released into the bile canaliculi (small canals) These join together to form the bile duct which transports the bile to the gall bladder
04142023 14
Liver Cells
Hepatocytes are unspecialised simple cuboidal shaped cells which have many microvilli on their surface
They are however involved in many metabolic functions including
Protein synthesis
Transformation
Storage of carbohydrates
Synthesis of cholesterol and bile salts
Detoxification and other processes
This means that their cytoplasm must be very dense and is specialised in the amounts of certain organelles that it contains
04142023 15
Kupffer cells
Kupffer cells are specialised macrophages moving about in the sinusoids involved in the breakdown and recycling of red blood cells A product it produces during breakdown is bilirubin which is excreted as part of the bile and in faces Bilirubin is the brown pigment is faeces
Application Scenario
A common condition in newborns jaundice refers to the yellow color of the skin and whites of the eyes caused by excess bilirubin in the blood
It is also seen in adults where an excess chronic consumption of alcohol can have damaging effects on your liver meaning that you are not removing bilirubin from your liver and bile ducts quickly enough as it builds up in the blood it is deposited in the skinhellip The resulting is jaundice
Daily requirement is 40-60g of protein but daily consumption is far more greater therefore breakdown of amino acids are needed as accumulation leads to toxicity
Two step process occurs in the liver before the amino acid component is excreted DEAMINATION
ORNITHINE CYCLE
04142023 19
Formation of Urea DEAMINATION
Removal of NH3 group fro the amino acid with oxygen forming a keto acid (-RCOCOOH) and Ammonia (NH3)
Ammonia is highly toxic and very soluble therefore should not be allowed to accumulate in the blood circulation
On removal of NH3 group energy is released
THE ORNITHINE CYCLE
Ammonia is converted into a less soluble and less toxic substance when combined with CO2 forming Urea
Urea is further passed into the blood circulation and into the kidneys where it is filtered out of the blood circulation and is concentrated in the urine
04142023 20
Detoxification
The liver detoxifies alcohol and drugs Toxins can also be rendered harmless by oxidation reduction methylation or a combination with another molecule
Liver cells contain many enzymes that enable rendering of toxic molecules less toxic form
This includes catalase which converts H2O2 to oxygen and water
DETOXIFICATION OF ALCOHOL
Alcohol is a CNS depressant contains a lot of energy that can be used for respiration STEP 1 Ethanol Ethanol dehydrogenase Ethanal (occurs in the hepatocytes)
The hydrogens release in the steps above are combined with NAD NADH
NAD is required to oxidise and breakdown fatty acids for use in respiration
04142023 21
Future Possible Complications
If the liver has to detoxify too much alcohol it has insufficient NAD to deal with the fatty acids
These fatty acids are converted back to lipids and are stored in the hepatocytes causing the liver to become enlarged
Causes a condition known as fatty liver alcohol-related hepatitis or cirrhosis
04142023 22
Stretching Your KnowledgeScenario
Liver cells contain a large group of enzymes called the cytochrome P450 enzymes These are responsible for the breakdown of some toxic molecules such as cocaine and other drugs (recreational and medicinal) The P450s are most concentrated in the endoplasmic reticulum of liver cells As a result of variation these enzymes can be more effective in some people than in others (Caucasian population compared to Afro-Caribean population)
Many drugs can be more effective in some people than in others and may also cause variable side effects
Task
1 Suggest why the P450s are most concentrated in the endoplasmic reticulum
2 Suggest why many medicinal drugs have different side effects in different people
3 Explain why the P450s are not identical in every person
The P450s are proteins these are manufactured by the ribosomes that are attached to the endoplasmic reticulum ndash they can be packaged in vesicles and transported to where they are needed
Each person may have slightly different enzymes (evolution) These may break the drugs down in a slightly different way producing different by-products (SEs)
Genetic variation means that different people will have different alleles ndash these will produce slightly different enzymes
04142023 23
Questions
1 Why must ammonia be converted to urea
2 Explain why excess amino acids and alcohol should not be excreted
3 Suggest why the liver cells have large number of mitochondria and ribosomes
Ammonia is highly soluble and very toxic urea is less soluble and less toxic
They contain valuable energy that can be converted to useable forms Some amino acids can be converted into other amino acids
The mitochondria provide ATP (metabolic energy) for the active or energy-requiring processes eg protein synthesis mitosis active transport endo and exocytosis The ribosomes manufacture the many enzymes that are needed in liver cells
04142023 24
124 The Kidney
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 7
Why must these substances be removedPart III
If the pH drops below 73 it results in slowed or difficult breathing headache
drowsiness restlessness tremor and confusion
May also be a rapid heart rate and changes in blood pressure
THIS IS RESPIRATORY ACIDOSIS (A MEDICAL EMERGENCY NEEDS TREATMENT IMMEDIATELY)
Respiratory acidosis can also be caused by diseases or conditions that affect the lungs themselves due to blockage of airway leading to increase in carbon dioxide These diseases include emphysema chronic bronchitis asthma or severe pneumonia Conditions such as swelling a foreign object or vomit in the airways are also causative
04142023 8
Why must these substances be removed
Part IV Nitrogenous Compounds
The body cannot store proteins or amino acids(aa) However aa contain as much energy as carbohydrates therefore we do not want to waste this energy source AA are transported to the liver and the potentially toxic amino group is removed (deamination)
Step 1 -The amino group initially forms a very soluble and highly toxic compound = ammonia
Amino acid + oxygen keto acid + ammonia
Step 2 - Ammonia is converted to a less soluble and less toxic compound = urea
Urea is then transported to the kidneys for excretion The remaining keto acid can be used directly in respiration to release its energy or it may be converted to a carbohydrate or fat for storage
04142023 9
122 The Liver
04142023 10
The structure of the liver
The liver cells namely the hepatocytes carry hundreds of metabolic processes and has an important role in homeostasis Therefore it is essential for a continuous supply of blood The internal structure of the liver is arranged to ensure that as much blood flows past as many liver cells as possible
04142023 11
Blood flow to the liver
TO
The liver has two blood supplies
Oxygenated blood from the heart Blood travels from the aorta via the HEPATIC ARTERY INTO THE LIVER
This supplies the oxygen essential for aerobic respiratory Hepatocytes are very active and require energy in the form of ATP so it is essential there is a good oxygen supply
Deoxygenated blood from the digestive system This enters the liver via the HEPATIC PORTAL VEIN This blood is rich in the products of digestion The concentration of the various compounds will be uncontrolled and the blood may contain toxic compounds that have been absorbed by the intestine
04142023 12
Blood flow from the liver
FROM Blood leaves the liver via the
HEPATIC VEIN This re-joins the vena cava and the blood returns to normal circulation
A Fourth vessel connected to the liver is not a blood vessel It is the bile duct Bile is a secretion from the liver It has both a digestive function and an excretory function The bile duct carries bile from the LIVER TO THE GALLBLADDER where it is stored until required to aid the digestion of fats in the small intestine
04142023 13
The arrangement of cells inside the liver
The liver is divided into lobes and further divided into cylindrical lobules
As the hepatic artery and hepatic portal vein enter the liver they split into smaller and smaller vessels which run parallel or between the lobules and are known as inter-lobular vessels
The blood from two blood vessels are mixed and passed through a special chamber called sinusoid which furthermore empty into the intra-lobular vessels a branch of the hepatic vein
The branches of the hepatic vein from different lobules join together to form the hepatic vein draining blood from the liver
As blood moves along the sinusoid it is in very close contact with the liver cells They are able to remove molecules from the blood and pass molecules into the blood
One of the many functions of the liver cells is to manufacture bile This is released into the bile canaliculi (small canals) These join together to form the bile duct which transports the bile to the gall bladder
04142023 14
Liver Cells
Hepatocytes are unspecialised simple cuboidal shaped cells which have many microvilli on their surface
They are however involved in many metabolic functions including
Protein synthesis
Transformation
Storage of carbohydrates
Synthesis of cholesterol and bile salts
Detoxification and other processes
This means that their cytoplasm must be very dense and is specialised in the amounts of certain organelles that it contains
04142023 15
Kupffer cells
Kupffer cells are specialised macrophages moving about in the sinusoids involved in the breakdown and recycling of red blood cells A product it produces during breakdown is bilirubin which is excreted as part of the bile and in faces Bilirubin is the brown pigment is faeces
Application Scenario
A common condition in newborns jaundice refers to the yellow color of the skin and whites of the eyes caused by excess bilirubin in the blood
It is also seen in adults where an excess chronic consumption of alcohol can have damaging effects on your liver meaning that you are not removing bilirubin from your liver and bile ducts quickly enough as it builds up in the blood it is deposited in the skinhellip The resulting is jaundice
Daily requirement is 40-60g of protein but daily consumption is far more greater therefore breakdown of amino acids are needed as accumulation leads to toxicity
Two step process occurs in the liver before the amino acid component is excreted DEAMINATION
ORNITHINE CYCLE
04142023 19
Formation of Urea DEAMINATION
Removal of NH3 group fro the amino acid with oxygen forming a keto acid (-RCOCOOH) and Ammonia (NH3)
Ammonia is highly toxic and very soluble therefore should not be allowed to accumulate in the blood circulation
On removal of NH3 group energy is released
THE ORNITHINE CYCLE
Ammonia is converted into a less soluble and less toxic substance when combined with CO2 forming Urea
Urea is further passed into the blood circulation and into the kidneys where it is filtered out of the blood circulation and is concentrated in the urine
04142023 20
Detoxification
The liver detoxifies alcohol and drugs Toxins can also be rendered harmless by oxidation reduction methylation or a combination with another molecule
Liver cells contain many enzymes that enable rendering of toxic molecules less toxic form
This includes catalase which converts H2O2 to oxygen and water
DETOXIFICATION OF ALCOHOL
Alcohol is a CNS depressant contains a lot of energy that can be used for respiration STEP 1 Ethanol Ethanol dehydrogenase Ethanal (occurs in the hepatocytes)
The hydrogens release in the steps above are combined with NAD NADH
NAD is required to oxidise and breakdown fatty acids for use in respiration
04142023 21
Future Possible Complications
If the liver has to detoxify too much alcohol it has insufficient NAD to deal with the fatty acids
These fatty acids are converted back to lipids and are stored in the hepatocytes causing the liver to become enlarged
Causes a condition known as fatty liver alcohol-related hepatitis or cirrhosis
04142023 22
Stretching Your KnowledgeScenario
Liver cells contain a large group of enzymes called the cytochrome P450 enzymes These are responsible for the breakdown of some toxic molecules such as cocaine and other drugs (recreational and medicinal) The P450s are most concentrated in the endoplasmic reticulum of liver cells As a result of variation these enzymes can be more effective in some people than in others (Caucasian population compared to Afro-Caribean population)
Many drugs can be more effective in some people than in others and may also cause variable side effects
Task
1 Suggest why the P450s are most concentrated in the endoplasmic reticulum
2 Suggest why many medicinal drugs have different side effects in different people
3 Explain why the P450s are not identical in every person
The P450s are proteins these are manufactured by the ribosomes that are attached to the endoplasmic reticulum ndash they can be packaged in vesicles and transported to where they are needed
Each person may have slightly different enzymes (evolution) These may break the drugs down in a slightly different way producing different by-products (SEs)
Genetic variation means that different people will have different alleles ndash these will produce slightly different enzymes
04142023 23
Questions
1 Why must ammonia be converted to urea
2 Explain why excess amino acids and alcohol should not be excreted
3 Suggest why the liver cells have large number of mitochondria and ribosomes
Ammonia is highly soluble and very toxic urea is less soluble and less toxic
They contain valuable energy that can be converted to useable forms Some amino acids can be converted into other amino acids
The mitochondria provide ATP (metabolic energy) for the active or energy-requiring processes eg protein synthesis mitosis active transport endo and exocytosis The ribosomes manufacture the many enzymes that are needed in liver cells
04142023 24
124 The Kidney
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 8
Why must these substances be removed
Part IV Nitrogenous Compounds
The body cannot store proteins or amino acids(aa) However aa contain as much energy as carbohydrates therefore we do not want to waste this energy source AA are transported to the liver and the potentially toxic amino group is removed (deamination)
Step 1 -The amino group initially forms a very soluble and highly toxic compound = ammonia
Amino acid + oxygen keto acid + ammonia
Step 2 - Ammonia is converted to a less soluble and less toxic compound = urea
Urea is then transported to the kidneys for excretion The remaining keto acid can be used directly in respiration to release its energy or it may be converted to a carbohydrate or fat for storage
04142023 9
122 The Liver
04142023 10
The structure of the liver
The liver cells namely the hepatocytes carry hundreds of metabolic processes and has an important role in homeostasis Therefore it is essential for a continuous supply of blood The internal structure of the liver is arranged to ensure that as much blood flows past as many liver cells as possible
04142023 11
Blood flow to the liver
TO
The liver has two blood supplies
Oxygenated blood from the heart Blood travels from the aorta via the HEPATIC ARTERY INTO THE LIVER
This supplies the oxygen essential for aerobic respiratory Hepatocytes are very active and require energy in the form of ATP so it is essential there is a good oxygen supply
Deoxygenated blood from the digestive system This enters the liver via the HEPATIC PORTAL VEIN This blood is rich in the products of digestion The concentration of the various compounds will be uncontrolled and the blood may contain toxic compounds that have been absorbed by the intestine
04142023 12
Blood flow from the liver
FROM Blood leaves the liver via the
HEPATIC VEIN This re-joins the vena cava and the blood returns to normal circulation
A Fourth vessel connected to the liver is not a blood vessel It is the bile duct Bile is a secretion from the liver It has both a digestive function and an excretory function The bile duct carries bile from the LIVER TO THE GALLBLADDER where it is stored until required to aid the digestion of fats in the small intestine
04142023 13
The arrangement of cells inside the liver
The liver is divided into lobes and further divided into cylindrical lobules
As the hepatic artery and hepatic portal vein enter the liver they split into smaller and smaller vessels which run parallel or between the lobules and are known as inter-lobular vessels
The blood from two blood vessels are mixed and passed through a special chamber called sinusoid which furthermore empty into the intra-lobular vessels a branch of the hepatic vein
The branches of the hepatic vein from different lobules join together to form the hepatic vein draining blood from the liver
As blood moves along the sinusoid it is in very close contact with the liver cells They are able to remove molecules from the blood and pass molecules into the blood
One of the many functions of the liver cells is to manufacture bile This is released into the bile canaliculi (small canals) These join together to form the bile duct which transports the bile to the gall bladder
04142023 14
Liver Cells
Hepatocytes are unspecialised simple cuboidal shaped cells which have many microvilli on their surface
They are however involved in many metabolic functions including
Protein synthesis
Transformation
Storage of carbohydrates
Synthesis of cholesterol and bile salts
Detoxification and other processes
This means that their cytoplasm must be very dense and is specialised in the amounts of certain organelles that it contains
04142023 15
Kupffer cells
Kupffer cells are specialised macrophages moving about in the sinusoids involved in the breakdown and recycling of red blood cells A product it produces during breakdown is bilirubin which is excreted as part of the bile and in faces Bilirubin is the brown pigment is faeces
Application Scenario
A common condition in newborns jaundice refers to the yellow color of the skin and whites of the eyes caused by excess bilirubin in the blood
It is also seen in adults where an excess chronic consumption of alcohol can have damaging effects on your liver meaning that you are not removing bilirubin from your liver and bile ducts quickly enough as it builds up in the blood it is deposited in the skinhellip The resulting is jaundice
Daily requirement is 40-60g of protein but daily consumption is far more greater therefore breakdown of amino acids are needed as accumulation leads to toxicity
Two step process occurs in the liver before the amino acid component is excreted DEAMINATION
ORNITHINE CYCLE
04142023 19
Formation of Urea DEAMINATION
Removal of NH3 group fro the amino acid with oxygen forming a keto acid (-RCOCOOH) and Ammonia (NH3)
Ammonia is highly toxic and very soluble therefore should not be allowed to accumulate in the blood circulation
On removal of NH3 group energy is released
THE ORNITHINE CYCLE
Ammonia is converted into a less soluble and less toxic substance when combined with CO2 forming Urea
Urea is further passed into the blood circulation and into the kidneys where it is filtered out of the blood circulation and is concentrated in the urine
04142023 20
Detoxification
The liver detoxifies alcohol and drugs Toxins can also be rendered harmless by oxidation reduction methylation or a combination with another molecule
Liver cells contain many enzymes that enable rendering of toxic molecules less toxic form
This includes catalase which converts H2O2 to oxygen and water
DETOXIFICATION OF ALCOHOL
Alcohol is a CNS depressant contains a lot of energy that can be used for respiration STEP 1 Ethanol Ethanol dehydrogenase Ethanal (occurs in the hepatocytes)
The hydrogens release in the steps above are combined with NAD NADH
NAD is required to oxidise and breakdown fatty acids for use in respiration
04142023 21
Future Possible Complications
If the liver has to detoxify too much alcohol it has insufficient NAD to deal with the fatty acids
These fatty acids are converted back to lipids and are stored in the hepatocytes causing the liver to become enlarged
Causes a condition known as fatty liver alcohol-related hepatitis or cirrhosis
04142023 22
Stretching Your KnowledgeScenario
Liver cells contain a large group of enzymes called the cytochrome P450 enzymes These are responsible for the breakdown of some toxic molecules such as cocaine and other drugs (recreational and medicinal) The P450s are most concentrated in the endoplasmic reticulum of liver cells As a result of variation these enzymes can be more effective in some people than in others (Caucasian population compared to Afro-Caribean population)
Many drugs can be more effective in some people than in others and may also cause variable side effects
Task
1 Suggest why the P450s are most concentrated in the endoplasmic reticulum
2 Suggest why many medicinal drugs have different side effects in different people
3 Explain why the P450s are not identical in every person
The P450s are proteins these are manufactured by the ribosomes that are attached to the endoplasmic reticulum ndash they can be packaged in vesicles and transported to where they are needed
Each person may have slightly different enzymes (evolution) These may break the drugs down in a slightly different way producing different by-products (SEs)
Genetic variation means that different people will have different alleles ndash these will produce slightly different enzymes
04142023 23
Questions
1 Why must ammonia be converted to urea
2 Explain why excess amino acids and alcohol should not be excreted
3 Suggest why the liver cells have large number of mitochondria and ribosomes
Ammonia is highly soluble and very toxic urea is less soluble and less toxic
They contain valuable energy that can be converted to useable forms Some amino acids can be converted into other amino acids
The mitochondria provide ATP (metabolic energy) for the active or energy-requiring processes eg protein synthesis mitosis active transport endo and exocytosis The ribosomes manufacture the many enzymes that are needed in liver cells
04142023 24
124 The Kidney
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 9
122 The Liver
04142023 10
The structure of the liver
The liver cells namely the hepatocytes carry hundreds of metabolic processes and has an important role in homeostasis Therefore it is essential for a continuous supply of blood The internal structure of the liver is arranged to ensure that as much blood flows past as many liver cells as possible
04142023 11
Blood flow to the liver
TO
The liver has two blood supplies
Oxygenated blood from the heart Blood travels from the aorta via the HEPATIC ARTERY INTO THE LIVER
This supplies the oxygen essential for aerobic respiratory Hepatocytes are very active and require energy in the form of ATP so it is essential there is a good oxygen supply
Deoxygenated blood from the digestive system This enters the liver via the HEPATIC PORTAL VEIN This blood is rich in the products of digestion The concentration of the various compounds will be uncontrolled and the blood may contain toxic compounds that have been absorbed by the intestine
04142023 12
Blood flow from the liver
FROM Blood leaves the liver via the
HEPATIC VEIN This re-joins the vena cava and the blood returns to normal circulation
A Fourth vessel connected to the liver is not a blood vessel It is the bile duct Bile is a secretion from the liver It has both a digestive function and an excretory function The bile duct carries bile from the LIVER TO THE GALLBLADDER where it is stored until required to aid the digestion of fats in the small intestine
04142023 13
The arrangement of cells inside the liver
The liver is divided into lobes and further divided into cylindrical lobules
As the hepatic artery and hepatic portal vein enter the liver they split into smaller and smaller vessels which run parallel or between the lobules and are known as inter-lobular vessels
The blood from two blood vessels are mixed and passed through a special chamber called sinusoid which furthermore empty into the intra-lobular vessels a branch of the hepatic vein
The branches of the hepatic vein from different lobules join together to form the hepatic vein draining blood from the liver
As blood moves along the sinusoid it is in very close contact with the liver cells They are able to remove molecules from the blood and pass molecules into the blood
One of the many functions of the liver cells is to manufacture bile This is released into the bile canaliculi (small canals) These join together to form the bile duct which transports the bile to the gall bladder
04142023 14
Liver Cells
Hepatocytes are unspecialised simple cuboidal shaped cells which have many microvilli on their surface
They are however involved in many metabolic functions including
Protein synthesis
Transformation
Storage of carbohydrates
Synthesis of cholesterol and bile salts
Detoxification and other processes
This means that their cytoplasm must be very dense and is specialised in the amounts of certain organelles that it contains
04142023 15
Kupffer cells
Kupffer cells are specialised macrophages moving about in the sinusoids involved in the breakdown and recycling of red blood cells A product it produces during breakdown is bilirubin which is excreted as part of the bile and in faces Bilirubin is the brown pigment is faeces
Application Scenario
A common condition in newborns jaundice refers to the yellow color of the skin and whites of the eyes caused by excess bilirubin in the blood
It is also seen in adults where an excess chronic consumption of alcohol can have damaging effects on your liver meaning that you are not removing bilirubin from your liver and bile ducts quickly enough as it builds up in the blood it is deposited in the skinhellip The resulting is jaundice
Daily requirement is 40-60g of protein but daily consumption is far more greater therefore breakdown of amino acids are needed as accumulation leads to toxicity
Two step process occurs in the liver before the amino acid component is excreted DEAMINATION
ORNITHINE CYCLE
04142023 19
Formation of Urea DEAMINATION
Removal of NH3 group fro the amino acid with oxygen forming a keto acid (-RCOCOOH) and Ammonia (NH3)
Ammonia is highly toxic and very soluble therefore should not be allowed to accumulate in the blood circulation
On removal of NH3 group energy is released
THE ORNITHINE CYCLE
Ammonia is converted into a less soluble and less toxic substance when combined with CO2 forming Urea
Urea is further passed into the blood circulation and into the kidneys where it is filtered out of the blood circulation and is concentrated in the urine
04142023 20
Detoxification
The liver detoxifies alcohol and drugs Toxins can also be rendered harmless by oxidation reduction methylation or a combination with another molecule
Liver cells contain many enzymes that enable rendering of toxic molecules less toxic form
This includes catalase which converts H2O2 to oxygen and water
DETOXIFICATION OF ALCOHOL
Alcohol is a CNS depressant contains a lot of energy that can be used for respiration STEP 1 Ethanol Ethanol dehydrogenase Ethanal (occurs in the hepatocytes)
The hydrogens release in the steps above are combined with NAD NADH
NAD is required to oxidise and breakdown fatty acids for use in respiration
04142023 21
Future Possible Complications
If the liver has to detoxify too much alcohol it has insufficient NAD to deal with the fatty acids
These fatty acids are converted back to lipids and are stored in the hepatocytes causing the liver to become enlarged
Causes a condition known as fatty liver alcohol-related hepatitis or cirrhosis
04142023 22
Stretching Your KnowledgeScenario
Liver cells contain a large group of enzymes called the cytochrome P450 enzymes These are responsible for the breakdown of some toxic molecules such as cocaine and other drugs (recreational and medicinal) The P450s are most concentrated in the endoplasmic reticulum of liver cells As a result of variation these enzymes can be more effective in some people than in others (Caucasian population compared to Afro-Caribean population)
Many drugs can be more effective in some people than in others and may also cause variable side effects
Task
1 Suggest why the P450s are most concentrated in the endoplasmic reticulum
2 Suggest why many medicinal drugs have different side effects in different people
3 Explain why the P450s are not identical in every person
The P450s are proteins these are manufactured by the ribosomes that are attached to the endoplasmic reticulum ndash they can be packaged in vesicles and transported to where they are needed
Each person may have slightly different enzymes (evolution) These may break the drugs down in a slightly different way producing different by-products (SEs)
Genetic variation means that different people will have different alleles ndash these will produce slightly different enzymes
04142023 23
Questions
1 Why must ammonia be converted to urea
2 Explain why excess amino acids and alcohol should not be excreted
3 Suggest why the liver cells have large number of mitochondria and ribosomes
Ammonia is highly soluble and very toxic urea is less soluble and less toxic
They contain valuable energy that can be converted to useable forms Some amino acids can be converted into other amino acids
The mitochondria provide ATP (metabolic energy) for the active or energy-requiring processes eg protein synthesis mitosis active transport endo and exocytosis The ribosomes manufacture the many enzymes that are needed in liver cells
04142023 24
124 The Kidney
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 10
The structure of the liver
The liver cells namely the hepatocytes carry hundreds of metabolic processes and has an important role in homeostasis Therefore it is essential for a continuous supply of blood The internal structure of the liver is arranged to ensure that as much blood flows past as many liver cells as possible
04142023 11
Blood flow to the liver
TO
The liver has two blood supplies
Oxygenated blood from the heart Blood travels from the aorta via the HEPATIC ARTERY INTO THE LIVER
This supplies the oxygen essential for aerobic respiratory Hepatocytes are very active and require energy in the form of ATP so it is essential there is a good oxygen supply
Deoxygenated blood from the digestive system This enters the liver via the HEPATIC PORTAL VEIN This blood is rich in the products of digestion The concentration of the various compounds will be uncontrolled and the blood may contain toxic compounds that have been absorbed by the intestine
04142023 12
Blood flow from the liver
FROM Blood leaves the liver via the
HEPATIC VEIN This re-joins the vena cava and the blood returns to normal circulation
A Fourth vessel connected to the liver is not a blood vessel It is the bile duct Bile is a secretion from the liver It has both a digestive function and an excretory function The bile duct carries bile from the LIVER TO THE GALLBLADDER where it is stored until required to aid the digestion of fats in the small intestine
04142023 13
The arrangement of cells inside the liver
The liver is divided into lobes and further divided into cylindrical lobules
As the hepatic artery and hepatic portal vein enter the liver they split into smaller and smaller vessels which run parallel or between the lobules and are known as inter-lobular vessels
The blood from two blood vessels are mixed and passed through a special chamber called sinusoid which furthermore empty into the intra-lobular vessels a branch of the hepatic vein
The branches of the hepatic vein from different lobules join together to form the hepatic vein draining blood from the liver
As blood moves along the sinusoid it is in very close contact with the liver cells They are able to remove molecules from the blood and pass molecules into the blood
One of the many functions of the liver cells is to manufacture bile This is released into the bile canaliculi (small canals) These join together to form the bile duct which transports the bile to the gall bladder
04142023 14
Liver Cells
Hepatocytes are unspecialised simple cuboidal shaped cells which have many microvilli on their surface
They are however involved in many metabolic functions including
Protein synthesis
Transformation
Storage of carbohydrates
Synthesis of cholesterol and bile salts
Detoxification and other processes
This means that their cytoplasm must be very dense and is specialised in the amounts of certain organelles that it contains
04142023 15
Kupffer cells
Kupffer cells are specialised macrophages moving about in the sinusoids involved in the breakdown and recycling of red blood cells A product it produces during breakdown is bilirubin which is excreted as part of the bile and in faces Bilirubin is the brown pigment is faeces
Application Scenario
A common condition in newborns jaundice refers to the yellow color of the skin and whites of the eyes caused by excess bilirubin in the blood
It is also seen in adults where an excess chronic consumption of alcohol can have damaging effects on your liver meaning that you are not removing bilirubin from your liver and bile ducts quickly enough as it builds up in the blood it is deposited in the skinhellip The resulting is jaundice
Daily requirement is 40-60g of protein but daily consumption is far more greater therefore breakdown of amino acids are needed as accumulation leads to toxicity
Two step process occurs in the liver before the amino acid component is excreted DEAMINATION
ORNITHINE CYCLE
04142023 19
Formation of Urea DEAMINATION
Removal of NH3 group fro the amino acid with oxygen forming a keto acid (-RCOCOOH) and Ammonia (NH3)
Ammonia is highly toxic and very soluble therefore should not be allowed to accumulate in the blood circulation
On removal of NH3 group energy is released
THE ORNITHINE CYCLE
Ammonia is converted into a less soluble and less toxic substance when combined with CO2 forming Urea
Urea is further passed into the blood circulation and into the kidneys where it is filtered out of the blood circulation and is concentrated in the urine
04142023 20
Detoxification
The liver detoxifies alcohol and drugs Toxins can also be rendered harmless by oxidation reduction methylation or a combination with another molecule
Liver cells contain many enzymes that enable rendering of toxic molecules less toxic form
This includes catalase which converts H2O2 to oxygen and water
DETOXIFICATION OF ALCOHOL
Alcohol is a CNS depressant contains a lot of energy that can be used for respiration STEP 1 Ethanol Ethanol dehydrogenase Ethanal (occurs in the hepatocytes)
The hydrogens release in the steps above are combined with NAD NADH
NAD is required to oxidise and breakdown fatty acids for use in respiration
04142023 21
Future Possible Complications
If the liver has to detoxify too much alcohol it has insufficient NAD to deal with the fatty acids
These fatty acids are converted back to lipids and are stored in the hepatocytes causing the liver to become enlarged
Causes a condition known as fatty liver alcohol-related hepatitis or cirrhosis
04142023 22
Stretching Your KnowledgeScenario
Liver cells contain a large group of enzymes called the cytochrome P450 enzymes These are responsible for the breakdown of some toxic molecules such as cocaine and other drugs (recreational and medicinal) The P450s are most concentrated in the endoplasmic reticulum of liver cells As a result of variation these enzymes can be more effective in some people than in others (Caucasian population compared to Afro-Caribean population)
Many drugs can be more effective in some people than in others and may also cause variable side effects
Task
1 Suggest why the P450s are most concentrated in the endoplasmic reticulum
2 Suggest why many medicinal drugs have different side effects in different people
3 Explain why the P450s are not identical in every person
The P450s are proteins these are manufactured by the ribosomes that are attached to the endoplasmic reticulum ndash they can be packaged in vesicles and transported to where they are needed
Each person may have slightly different enzymes (evolution) These may break the drugs down in a slightly different way producing different by-products (SEs)
Genetic variation means that different people will have different alleles ndash these will produce slightly different enzymes
04142023 23
Questions
1 Why must ammonia be converted to urea
2 Explain why excess amino acids and alcohol should not be excreted
3 Suggest why the liver cells have large number of mitochondria and ribosomes
Ammonia is highly soluble and very toxic urea is less soluble and less toxic
They contain valuable energy that can be converted to useable forms Some amino acids can be converted into other amino acids
The mitochondria provide ATP (metabolic energy) for the active or energy-requiring processes eg protein synthesis mitosis active transport endo and exocytosis The ribosomes manufacture the many enzymes that are needed in liver cells
04142023 24
124 The Kidney
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 11
Blood flow to the liver
TO
The liver has two blood supplies
Oxygenated blood from the heart Blood travels from the aorta via the HEPATIC ARTERY INTO THE LIVER
This supplies the oxygen essential for aerobic respiratory Hepatocytes are very active and require energy in the form of ATP so it is essential there is a good oxygen supply
Deoxygenated blood from the digestive system This enters the liver via the HEPATIC PORTAL VEIN This blood is rich in the products of digestion The concentration of the various compounds will be uncontrolled and the blood may contain toxic compounds that have been absorbed by the intestine
04142023 12
Blood flow from the liver
FROM Blood leaves the liver via the
HEPATIC VEIN This re-joins the vena cava and the blood returns to normal circulation
A Fourth vessel connected to the liver is not a blood vessel It is the bile duct Bile is a secretion from the liver It has both a digestive function and an excretory function The bile duct carries bile from the LIVER TO THE GALLBLADDER where it is stored until required to aid the digestion of fats in the small intestine
04142023 13
The arrangement of cells inside the liver
The liver is divided into lobes and further divided into cylindrical lobules
As the hepatic artery and hepatic portal vein enter the liver they split into smaller and smaller vessels which run parallel or between the lobules and are known as inter-lobular vessels
The blood from two blood vessels are mixed and passed through a special chamber called sinusoid which furthermore empty into the intra-lobular vessels a branch of the hepatic vein
The branches of the hepatic vein from different lobules join together to form the hepatic vein draining blood from the liver
As blood moves along the sinusoid it is in very close contact with the liver cells They are able to remove molecules from the blood and pass molecules into the blood
One of the many functions of the liver cells is to manufacture bile This is released into the bile canaliculi (small canals) These join together to form the bile duct which transports the bile to the gall bladder
04142023 14
Liver Cells
Hepatocytes are unspecialised simple cuboidal shaped cells which have many microvilli on their surface
They are however involved in many metabolic functions including
Protein synthesis
Transformation
Storage of carbohydrates
Synthesis of cholesterol and bile salts
Detoxification and other processes
This means that their cytoplasm must be very dense and is specialised in the amounts of certain organelles that it contains
04142023 15
Kupffer cells
Kupffer cells are specialised macrophages moving about in the sinusoids involved in the breakdown and recycling of red blood cells A product it produces during breakdown is bilirubin which is excreted as part of the bile and in faces Bilirubin is the brown pigment is faeces
Application Scenario
A common condition in newborns jaundice refers to the yellow color of the skin and whites of the eyes caused by excess bilirubin in the blood
It is also seen in adults where an excess chronic consumption of alcohol can have damaging effects on your liver meaning that you are not removing bilirubin from your liver and bile ducts quickly enough as it builds up in the blood it is deposited in the skinhellip The resulting is jaundice
Daily requirement is 40-60g of protein but daily consumption is far more greater therefore breakdown of amino acids are needed as accumulation leads to toxicity
Two step process occurs in the liver before the amino acid component is excreted DEAMINATION
ORNITHINE CYCLE
04142023 19
Formation of Urea DEAMINATION
Removal of NH3 group fro the amino acid with oxygen forming a keto acid (-RCOCOOH) and Ammonia (NH3)
Ammonia is highly toxic and very soluble therefore should not be allowed to accumulate in the blood circulation
On removal of NH3 group energy is released
THE ORNITHINE CYCLE
Ammonia is converted into a less soluble and less toxic substance when combined with CO2 forming Urea
Urea is further passed into the blood circulation and into the kidneys where it is filtered out of the blood circulation and is concentrated in the urine
04142023 20
Detoxification
The liver detoxifies alcohol and drugs Toxins can also be rendered harmless by oxidation reduction methylation or a combination with another molecule
Liver cells contain many enzymes that enable rendering of toxic molecules less toxic form
This includes catalase which converts H2O2 to oxygen and water
DETOXIFICATION OF ALCOHOL
Alcohol is a CNS depressant contains a lot of energy that can be used for respiration STEP 1 Ethanol Ethanol dehydrogenase Ethanal (occurs in the hepatocytes)
The hydrogens release in the steps above are combined with NAD NADH
NAD is required to oxidise and breakdown fatty acids for use in respiration
04142023 21
Future Possible Complications
If the liver has to detoxify too much alcohol it has insufficient NAD to deal with the fatty acids
These fatty acids are converted back to lipids and are stored in the hepatocytes causing the liver to become enlarged
Causes a condition known as fatty liver alcohol-related hepatitis or cirrhosis
04142023 22
Stretching Your KnowledgeScenario
Liver cells contain a large group of enzymes called the cytochrome P450 enzymes These are responsible for the breakdown of some toxic molecules such as cocaine and other drugs (recreational and medicinal) The P450s are most concentrated in the endoplasmic reticulum of liver cells As a result of variation these enzymes can be more effective in some people than in others (Caucasian population compared to Afro-Caribean population)
Many drugs can be more effective in some people than in others and may also cause variable side effects
Task
1 Suggest why the P450s are most concentrated in the endoplasmic reticulum
2 Suggest why many medicinal drugs have different side effects in different people
3 Explain why the P450s are not identical in every person
The P450s are proteins these are manufactured by the ribosomes that are attached to the endoplasmic reticulum ndash they can be packaged in vesicles and transported to where they are needed
Each person may have slightly different enzymes (evolution) These may break the drugs down in a slightly different way producing different by-products (SEs)
Genetic variation means that different people will have different alleles ndash these will produce slightly different enzymes
04142023 23
Questions
1 Why must ammonia be converted to urea
2 Explain why excess amino acids and alcohol should not be excreted
3 Suggest why the liver cells have large number of mitochondria and ribosomes
Ammonia is highly soluble and very toxic urea is less soluble and less toxic
They contain valuable energy that can be converted to useable forms Some amino acids can be converted into other amino acids
The mitochondria provide ATP (metabolic energy) for the active or energy-requiring processes eg protein synthesis mitosis active transport endo and exocytosis The ribosomes manufacture the many enzymes that are needed in liver cells
04142023 24
124 The Kidney
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 12
Blood flow from the liver
FROM Blood leaves the liver via the
HEPATIC VEIN This re-joins the vena cava and the blood returns to normal circulation
A Fourth vessel connected to the liver is not a blood vessel It is the bile duct Bile is a secretion from the liver It has both a digestive function and an excretory function The bile duct carries bile from the LIVER TO THE GALLBLADDER where it is stored until required to aid the digestion of fats in the small intestine
04142023 13
The arrangement of cells inside the liver
The liver is divided into lobes and further divided into cylindrical lobules
As the hepatic artery and hepatic portal vein enter the liver they split into smaller and smaller vessels which run parallel or between the lobules and are known as inter-lobular vessels
The blood from two blood vessels are mixed and passed through a special chamber called sinusoid which furthermore empty into the intra-lobular vessels a branch of the hepatic vein
The branches of the hepatic vein from different lobules join together to form the hepatic vein draining blood from the liver
As blood moves along the sinusoid it is in very close contact with the liver cells They are able to remove molecules from the blood and pass molecules into the blood
One of the many functions of the liver cells is to manufacture bile This is released into the bile canaliculi (small canals) These join together to form the bile duct which transports the bile to the gall bladder
04142023 14
Liver Cells
Hepatocytes are unspecialised simple cuboidal shaped cells which have many microvilli on their surface
They are however involved in many metabolic functions including
Protein synthesis
Transformation
Storage of carbohydrates
Synthesis of cholesterol and bile salts
Detoxification and other processes
This means that their cytoplasm must be very dense and is specialised in the amounts of certain organelles that it contains
04142023 15
Kupffer cells
Kupffer cells are specialised macrophages moving about in the sinusoids involved in the breakdown and recycling of red blood cells A product it produces during breakdown is bilirubin which is excreted as part of the bile and in faces Bilirubin is the brown pigment is faeces
Application Scenario
A common condition in newborns jaundice refers to the yellow color of the skin and whites of the eyes caused by excess bilirubin in the blood
It is also seen in adults where an excess chronic consumption of alcohol can have damaging effects on your liver meaning that you are not removing bilirubin from your liver and bile ducts quickly enough as it builds up in the blood it is deposited in the skinhellip The resulting is jaundice
Daily requirement is 40-60g of protein but daily consumption is far more greater therefore breakdown of amino acids are needed as accumulation leads to toxicity
Two step process occurs in the liver before the amino acid component is excreted DEAMINATION
ORNITHINE CYCLE
04142023 19
Formation of Urea DEAMINATION
Removal of NH3 group fro the amino acid with oxygen forming a keto acid (-RCOCOOH) and Ammonia (NH3)
Ammonia is highly toxic and very soluble therefore should not be allowed to accumulate in the blood circulation
On removal of NH3 group energy is released
THE ORNITHINE CYCLE
Ammonia is converted into a less soluble and less toxic substance when combined with CO2 forming Urea
Urea is further passed into the blood circulation and into the kidneys where it is filtered out of the blood circulation and is concentrated in the urine
04142023 20
Detoxification
The liver detoxifies alcohol and drugs Toxins can also be rendered harmless by oxidation reduction methylation or a combination with another molecule
Liver cells contain many enzymes that enable rendering of toxic molecules less toxic form
This includes catalase which converts H2O2 to oxygen and water
DETOXIFICATION OF ALCOHOL
Alcohol is a CNS depressant contains a lot of energy that can be used for respiration STEP 1 Ethanol Ethanol dehydrogenase Ethanal (occurs in the hepatocytes)
The hydrogens release in the steps above are combined with NAD NADH
NAD is required to oxidise and breakdown fatty acids for use in respiration
04142023 21
Future Possible Complications
If the liver has to detoxify too much alcohol it has insufficient NAD to deal with the fatty acids
These fatty acids are converted back to lipids and are stored in the hepatocytes causing the liver to become enlarged
Causes a condition known as fatty liver alcohol-related hepatitis or cirrhosis
04142023 22
Stretching Your KnowledgeScenario
Liver cells contain a large group of enzymes called the cytochrome P450 enzymes These are responsible for the breakdown of some toxic molecules such as cocaine and other drugs (recreational and medicinal) The P450s are most concentrated in the endoplasmic reticulum of liver cells As a result of variation these enzymes can be more effective in some people than in others (Caucasian population compared to Afro-Caribean population)
Many drugs can be more effective in some people than in others and may also cause variable side effects
Task
1 Suggest why the P450s are most concentrated in the endoplasmic reticulum
2 Suggest why many medicinal drugs have different side effects in different people
3 Explain why the P450s are not identical in every person
The P450s are proteins these are manufactured by the ribosomes that are attached to the endoplasmic reticulum ndash they can be packaged in vesicles and transported to where they are needed
Each person may have slightly different enzymes (evolution) These may break the drugs down in a slightly different way producing different by-products (SEs)
Genetic variation means that different people will have different alleles ndash these will produce slightly different enzymes
04142023 23
Questions
1 Why must ammonia be converted to urea
2 Explain why excess amino acids and alcohol should not be excreted
3 Suggest why the liver cells have large number of mitochondria and ribosomes
Ammonia is highly soluble and very toxic urea is less soluble and less toxic
They contain valuable energy that can be converted to useable forms Some amino acids can be converted into other amino acids
The mitochondria provide ATP (metabolic energy) for the active or energy-requiring processes eg protein synthesis mitosis active transport endo and exocytosis The ribosomes manufacture the many enzymes that are needed in liver cells
04142023 24
124 The Kidney
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 13
The arrangement of cells inside the liver
The liver is divided into lobes and further divided into cylindrical lobules
As the hepatic artery and hepatic portal vein enter the liver they split into smaller and smaller vessels which run parallel or between the lobules and are known as inter-lobular vessels
The blood from two blood vessels are mixed and passed through a special chamber called sinusoid which furthermore empty into the intra-lobular vessels a branch of the hepatic vein
The branches of the hepatic vein from different lobules join together to form the hepatic vein draining blood from the liver
As blood moves along the sinusoid it is in very close contact with the liver cells They are able to remove molecules from the blood and pass molecules into the blood
One of the many functions of the liver cells is to manufacture bile This is released into the bile canaliculi (small canals) These join together to form the bile duct which transports the bile to the gall bladder
04142023 14
Liver Cells
Hepatocytes are unspecialised simple cuboidal shaped cells which have many microvilli on their surface
They are however involved in many metabolic functions including
Protein synthesis
Transformation
Storage of carbohydrates
Synthesis of cholesterol and bile salts
Detoxification and other processes
This means that their cytoplasm must be very dense and is specialised in the amounts of certain organelles that it contains
04142023 15
Kupffer cells
Kupffer cells are specialised macrophages moving about in the sinusoids involved in the breakdown and recycling of red blood cells A product it produces during breakdown is bilirubin which is excreted as part of the bile and in faces Bilirubin is the brown pigment is faeces
Application Scenario
A common condition in newborns jaundice refers to the yellow color of the skin and whites of the eyes caused by excess bilirubin in the blood
It is also seen in adults where an excess chronic consumption of alcohol can have damaging effects on your liver meaning that you are not removing bilirubin from your liver and bile ducts quickly enough as it builds up in the blood it is deposited in the skinhellip The resulting is jaundice
Daily requirement is 40-60g of protein but daily consumption is far more greater therefore breakdown of amino acids are needed as accumulation leads to toxicity
Two step process occurs in the liver before the amino acid component is excreted DEAMINATION
ORNITHINE CYCLE
04142023 19
Formation of Urea DEAMINATION
Removal of NH3 group fro the amino acid with oxygen forming a keto acid (-RCOCOOH) and Ammonia (NH3)
Ammonia is highly toxic and very soluble therefore should not be allowed to accumulate in the blood circulation
On removal of NH3 group energy is released
THE ORNITHINE CYCLE
Ammonia is converted into a less soluble and less toxic substance when combined with CO2 forming Urea
Urea is further passed into the blood circulation and into the kidneys where it is filtered out of the blood circulation and is concentrated in the urine
04142023 20
Detoxification
The liver detoxifies alcohol and drugs Toxins can also be rendered harmless by oxidation reduction methylation or a combination with another molecule
Liver cells contain many enzymes that enable rendering of toxic molecules less toxic form
This includes catalase which converts H2O2 to oxygen and water
DETOXIFICATION OF ALCOHOL
Alcohol is a CNS depressant contains a lot of energy that can be used for respiration STEP 1 Ethanol Ethanol dehydrogenase Ethanal (occurs in the hepatocytes)
The hydrogens release in the steps above are combined with NAD NADH
NAD is required to oxidise and breakdown fatty acids for use in respiration
04142023 21
Future Possible Complications
If the liver has to detoxify too much alcohol it has insufficient NAD to deal with the fatty acids
These fatty acids are converted back to lipids and are stored in the hepatocytes causing the liver to become enlarged
Causes a condition known as fatty liver alcohol-related hepatitis or cirrhosis
04142023 22
Stretching Your KnowledgeScenario
Liver cells contain a large group of enzymes called the cytochrome P450 enzymes These are responsible for the breakdown of some toxic molecules such as cocaine and other drugs (recreational and medicinal) The P450s are most concentrated in the endoplasmic reticulum of liver cells As a result of variation these enzymes can be more effective in some people than in others (Caucasian population compared to Afro-Caribean population)
Many drugs can be more effective in some people than in others and may also cause variable side effects
Task
1 Suggest why the P450s are most concentrated in the endoplasmic reticulum
2 Suggest why many medicinal drugs have different side effects in different people
3 Explain why the P450s are not identical in every person
The P450s are proteins these are manufactured by the ribosomes that are attached to the endoplasmic reticulum ndash they can be packaged in vesicles and transported to where they are needed
Each person may have slightly different enzymes (evolution) These may break the drugs down in a slightly different way producing different by-products (SEs)
Genetic variation means that different people will have different alleles ndash these will produce slightly different enzymes
04142023 23
Questions
1 Why must ammonia be converted to urea
2 Explain why excess amino acids and alcohol should not be excreted
3 Suggest why the liver cells have large number of mitochondria and ribosomes
Ammonia is highly soluble and very toxic urea is less soluble and less toxic
They contain valuable energy that can be converted to useable forms Some amino acids can be converted into other amino acids
The mitochondria provide ATP (metabolic energy) for the active or energy-requiring processes eg protein synthesis mitosis active transport endo and exocytosis The ribosomes manufacture the many enzymes that are needed in liver cells
04142023 24
124 The Kidney
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 14
Liver Cells
Hepatocytes are unspecialised simple cuboidal shaped cells which have many microvilli on their surface
They are however involved in many metabolic functions including
Protein synthesis
Transformation
Storage of carbohydrates
Synthesis of cholesterol and bile salts
Detoxification and other processes
This means that their cytoplasm must be very dense and is specialised in the amounts of certain organelles that it contains
04142023 15
Kupffer cells
Kupffer cells are specialised macrophages moving about in the sinusoids involved in the breakdown and recycling of red blood cells A product it produces during breakdown is bilirubin which is excreted as part of the bile and in faces Bilirubin is the brown pigment is faeces
Application Scenario
A common condition in newborns jaundice refers to the yellow color of the skin and whites of the eyes caused by excess bilirubin in the blood
It is also seen in adults where an excess chronic consumption of alcohol can have damaging effects on your liver meaning that you are not removing bilirubin from your liver and bile ducts quickly enough as it builds up in the blood it is deposited in the skinhellip The resulting is jaundice
Daily requirement is 40-60g of protein but daily consumption is far more greater therefore breakdown of amino acids are needed as accumulation leads to toxicity
Two step process occurs in the liver before the amino acid component is excreted DEAMINATION
ORNITHINE CYCLE
04142023 19
Formation of Urea DEAMINATION
Removal of NH3 group fro the amino acid with oxygen forming a keto acid (-RCOCOOH) and Ammonia (NH3)
Ammonia is highly toxic and very soluble therefore should not be allowed to accumulate in the blood circulation
On removal of NH3 group energy is released
THE ORNITHINE CYCLE
Ammonia is converted into a less soluble and less toxic substance when combined with CO2 forming Urea
Urea is further passed into the blood circulation and into the kidneys where it is filtered out of the blood circulation and is concentrated in the urine
04142023 20
Detoxification
The liver detoxifies alcohol and drugs Toxins can also be rendered harmless by oxidation reduction methylation or a combination with another molecule
Liver cells contain many enzymes that enable rendering of toxic molecules less toxic form
This includes catalase which converts H2O2 to oxygen and water
DETOXIFICATION OF ALCOHOL
Alcohol is a CNS depressant contains a lot of energy that can be used for respiration STEP 1 Ethanol Ethanol dehydrogenase Ethanal (occurs in the hepatocytes)
The hydrogens release in the steps above are combined with NAD NADH
NAD is required to oxidise and breakdown fatty acids for use in respiration
04142023 21
Future Possible Complications
If the liver has to detoxify too much alcohol it has insufficient NAD to deal with the fatty acids
These fatty acids are converted back to lipids and are stored in the hepatocytes causing the liver to become enlarged
Causes a condition known as fatty liver alcohol-related hepatitis or cirrhosis
04142023 22
Stretching Your KnowledgeScenario
Liver cells contain a large group of enzymes called the cytochrome P450 enzymes These are responsible for the breakdown of some toxic molecules such as cocaine and other drugs (recreational and medicinal) The P450s are most concentrated in the endoplasmic reticulum of liver cells As a result of variation these enzymes can be more effective in some people than in others (Caucasian population compared to Afro-Caribean population)
Many drugs can be more effective in some people than in others and may also cause variable side effects
Task
1 Suggest why the P450s are most concentrated in the endoplasmic reticulum
2 Suggest why many medicinal drugs have different side effects in different people
3 Explain why the P450s are not identical in every person
The P450s are proteins these are manufactured by the ribosomes that are attached to the endoplasmic reticulum ndash they can be packaged in vesicles and transported to where they are needed
Each person may have slightly different enzymes (evolution) These may break the drugs down in a slightly different way producing different by-products (SEs)
Genetic variation means that different people will have different alleles ndash these will produce slightly different enzymes
04142023 23
Questions
1 Why must ammonia be converted to urea
2 Explain why excess amino acids and alcohol should not be excreted
3 Suggest why the liver cells have large number of mitochondria and ribosomes
Ammonia is highly soluble and very toxic urea is less soluble and less toxic
They contain valuable energy that can be converted to useable forms Some amino acids can be converted into other amino acids
The mitochondria provide ATP (metabolic energy) for the active or energy-requiring processes eg protein synthesis mitosis active transport endo and exocytosis The ribosomes manufacture the many enzymes that are needed in liver cells
04142023 24
124 The Kidney
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 15
Kupffer cells
Kupffer cells are specialised macrophages moving about in the sinusoids involved in the breakdown and recycling of red blood cells A product it produces during breakdown is bilirubin which is excreted as part of the bile and in faces Bilirubin is the brown pigment is faeces
Application Scenario
A common condition in newborns jaundice refers to the yellow color of the skin and whites of the eyes caused by excess bilirubin in the blood
It is also seen in adults where an excess chronic consumption of alcohol can have damaging effects on your liver meaning that you are not removing bilirubin from your liver and bile ducts quickly enough as it builds up in the blood it is deposited in the skinhellip The resulting is jaundice
Daily requirement is 40-60g of protein but daily consumption is far more greater therefore breakdown of amino acids are needed as accumulation leads to toxicity
Two step process occurs in the liver before the amino acid component is excreted DEAMINATION
ORNITHINE CYCLE
04142023 19
Formation of Urea DEAMINATION
Removal of NH3 group fro the amino acid with oxygen forming a keto acid (-RCOCOOH) and Ammonia (NH3)
Ammonia is highly toxic and very soluble therefore should not be allowed to accumulate in the blood circulation
On removal of NH3 group energy is released
THE ORNITHINE CYCLE
Ammonia is converted into a less soluble and less toxic substance when combined with CO2 forming Urea
Urea is further passed into the blood circulation and into the kidneys where it is filtered out of the blood circulation and is concentrated in the urine
04142023 20
Detoxification
The liver detoxifies alcohol and drugs Toxins can also be rendered harmless by oxidation reduction methylation or a combination with another molecule
Liver cells contain many enzymes that enable rendering of toxic molecules less toxic form
This includes catalase which converts H2O2 to oxygen and water
DETOXIFICATION OF ALCOHOL
Alcohol is a CNS depressant contains a lot of energy that can be used for respiration STEP 1 Ethanol Ethanol dehydrogenase Ethanal (occurs in the hepatocytes)
The hydrogens release in the steps above are combined with NAD NADH
NAD is required to oxidise and breakdown fatty acids for use in respiration
04142023 21
Future Possible Complications
If the liver has to detoxify too much alcohol it has insufficient NAD to deal with the fatty acids
These fatty acids are converted back to lipids and are stored in the hepatocytes causing the liver to become enlarged
Causes a condition known as fatty liver alcohol-related hepatitis or cirrhosis
04142023 22
Stretching Your KnowledgeScenario
Liver cells contain a large group of enzymes called the cytochrome P450 enzymes These are responsible for the breakdown of some toxic molecules such as cocaine and other drugs (recreational and medicinal) The P450s are most concentrated in the endoplasmic reticulum of liver cells As a result of variation these enzymes can be more effective in some people than in others (Caucasian population compared to Afro-Caribean population)
Many drugs can be more effective in some people than in others and may also cause variable side effects
Task
1 Suggest why the P450s are most concentrated in the endoplasmic reticulum
2 Suggest why many medicinal drugs have different side effects in different people
3 Explain why the P450s are not identical in every person
The P450s are proteins these are manufactured by the ribosomes that are attached to the endoplasmic reticulum ndash they can be packaged in vesicles and transported to where they are needed
Each person may have slightly different enzymes (evolution) These may break the drugs down in a slightly different way producing different by-products (SEs)
Genetic variation means that different people will have different alleles ndash these will produce slightly different enzymes
04142023 23
Questions
1 Why must ammonia be converted to urea
2 Explain why excess amino acids and alcohol should not be excreted
3 Suggest why the liver cells have large number of mitochondria and ribosomes
Ammonia is highly soluble and very toxic urea is less soluble and less toxic
They contain valuable energy that can be converted to useable forms Some amino acids can be converted into other amino acids
The mitochondria provide ATP (metabolic energy) for the active or energy-requiring processes eg protein synthesis mitosis active transport endo and exocytosis The ribosomes manufacture the many enzymes that are needed in liver cells
04142023 24
124 The Kidney
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Daily requirement is 40-60g of protein but daily consumption is far more greater therefore breakdown of amino acids are needed as accumulation leads to toxicity
Two step process occurs in the liver before the amino acid component is excreted DEAMINATION
ORNITHINE CYCLE
04142023 19
Formation of Urea DEAMINATION
Removal of NH3 group fro the amino acid with oxygen forming a keto acid (-RCOCOOH) and Ammonia (NH3)
Ammonia is highly toxic and very soluble therefore should not be allowed to accumulate in the blood circulation
On removal of NH3 group energy is released
THE ORNITHINE CYCLE
Ammonia is converted into a less soluble and less toxic substance when combined with CO2 forming Urea
Urea is further passed into the blood circulation and into the kidneys where it is filtered out of the blood circulation and is concentrated in the urine
04142023 20
Detoxification
The liver detoxifies alcohol and drugs Toxins can also be rendered harmless by oxidation reduction methylation or a combination with another molecule
Liver cells contain many enzymes that enable rendering of toxic molecules less toxic form
This includes catalase which converts H2O2 to oxygen and water
DETOXIFICATION OF ALCOHOL
Alcohol is a CNS depressant contains a lot of energy that can be used for respiration STEP 1 Ethanol Ethanol dehydrogenase Ethanal (occurs in the hepatocytes)
The hydrogens release in the steps above are combined with NAD NADH
NAD is required to oxidise and breakdown fatty acids for use in respiration
04142023 21
Future Possible Complications
If the liver has to detoxify too much alcohol it has insufficient NAD to deal with the fatty acids
These fatty acids are converted back to lipids and are stored in the hepatocytes causing the liver to become enlarged
Causes a condition known as fatty liver alcohol-related hepatitis or cirrhosis
04142023 22
Stretching Your KnowledgeScenario
Liver cells contain a large group of enzymes called the cytochrome P450 enzymes These are responsible for the breakdown of some toxic molecules such as cocaine and other drugs (recreational and medicinal) The P450s are most concentrated in the endoplasmic reticulum of liver cells As a result of variation these enzymes can be more effective in some people than in others (Caucasian population compared to Afro-Caribean population)
Many drugs can be more effective in some people than in others and may also cause variable side effects
Task
1 Suggest why the P450s are most concentrated in the endoplasmic reticulum
2 Suggest why many medicinal drugs have different side effects in different people
3 Explain why the P450s are not identical in every person
The P450s are proteins these are manufactured by the ribosomes that are attached to the endoplasmic reticulum ndash they can be packaged in vesicles and transported to where they are needed
Each person may have slightly different enzymes (evolution) These may break the drugs down in a slightly different way producing different by-products (SEs)
Genetic variation means that different people will have different alleles ndash these will produce slightly different enzymes
04142023 23
Questions
1 Why must ammonia be converted to urea
2 Explain why excess amino acids and alcohol should not be excreted
3 Suggest why the liver cells have large number of mitochondria and ribosomes
Ammonia is highly soluble and very toxic urea is less soluble and less toxic
They contain valuable energy that can be converted to useable forms Some amino acids can be converted into other amino acids
The mitochondria provide ATP (metabolic energy) for the active or energy-requiring processes eg protein synthesis mitosis active transport endo and exocytosis The ribosomes manufacture the many enzymes that are needed in liver cells
04142023 24
124 The Kidney
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Daily requirement is 40-60g of protein but daily consumption is far more greater therefore breakdown of amino acids are needed as accumulation leads to toxicity
Two step process occurs in the liver before the amino acid component is excreted DEAMINATION
ORNITHINE CYCLE
04142023 19
Formation of Urea DEAMINATION
Removal of NH3 group fro the amino acid with oxygen forming a keto acid (-RCOCOOH) and Ammonia (NH3)
Ammonia is highly toxic and very soluble therefore should not be allowed to accumulate in the blood circulation
On removal of NH3 group energy is released
THE ORNITHINE CYCLE
Ammonia is converted into a less soluble and less toxic substance when combined with CO2 forming Urea
Urea is further passed into the blood circulation and into the kidneys where it is filtered out of the blood circulation and is concentrated in the urine
04142023 20
Detoxification
The liver detoxifies alcohol and drugs Toxins can also be rendered harmless by oxidation reduction methylation or a combination with another molecule
Liver cells contain many enzymes that enable rendering of toxic molecules less toxic form
This includes catalase which converts H2O2 to oxygen and water
DETOXIFICATION OF ALCOHOL
Alcohol is a CNS depressant contains a lot of energy that can be used for respiration STEP 1 Ethanol Ethanol dehydrogenase Ethanal (occurs in the hepatocytes)
The hydrogens release in the steps above are combined with NAD NADH
NAD is required to oxidise and breakdown fatty acids for use in respiration
04142023 21
Future Possible Complications
If the liver has to detoxify too much alcohol it has insufficient NAD to deal with the fatty acids
These fatty acids are converted back to lipids and are stored in the hepatocytes causing the liver to become enlarged
Causes a condition known as fatty liver alcohol-related hepatitis or cirrhosis
04142023 22
Stretching Your KnowledgeScenario
Liver cells contain a large group of enzymes called the cytochrome P450 enzymes These are responsible for the breakdown of some toxic molecules such as cocaine and other drugs (recreational and medicinal) The P450s are most concentrated in the endoplasmic reticulum of liver cells As a result of variation these enzymes can be more effective in some people than in others (Caucasian population compared to Afro-Caribean population)
Many drugs can be more effective in some people than in others and may also cause variable side effects
Task
1 Suggest why the P450s are most concentrated in the endoplasmic reticulum
2 Suggest why many medicinal drugs have different side effects in different people
3 Explain why the P450s are not identical in every person
The P450s are proteins these are manufactured by the ribosomes that are attached to the endoplasmic reticulum ndash they can be packaged in vesicles and transported to where they are needed
Each person may have slightly different enzymes (evolution) These may break the drugs down in a slightly different way producing different by-products (SEs)
Genetic variation means that different people will have different alleles ndash these will produce slightly different enzymes
04142023 23
Questions
1 Why must ammonia be converted to urea
2 Explain why excess amino acids and alcohol should not be excreted
3 Suggest why the liver cells have large number of mitochondria and ribosomes
Ammonia is highly soluble and very toxic urea is less soluble and less toxic
They contain valuable energy that can be converted to useable forms Some amino acids can be converted into other amino acids
The mitochondria provide ATP (metabolic energy) for the active or energy-requiring processes eg protein synthesis mitosis active transport endo and exocytosis The ribosomes manufacture the many enzymes that are needed in liver cells
04142023 24
124 The Kidney
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 18
Formation of Urea
Daily requirement is 40-60g of protein but daily consumption is far more greater therefore breakdown of amino acids are needed as accumulation leads to toxicity
Two step process occurs in the liver before the amino acid component is excreted DEAMINATION
ORNITHINE CYCLE
04142023 19
Formation of Urea DEAMINATION
Removal of NH3 group fro the amino acid with oxygen forming a keto acid (-RCOCOOH) and Ammonia (NH3)
Ammonia is highly toxic and very soluble therefore should not be allowed to accumulate in the blood circulation
On removal of NH3 group energy is released
THE ORNITHINE CYCLE
Ammonia is converted into a less soluble and less toxic substance when combined with CO2 forming Urea
Urea is further passed into the blood circulation and into the kidneys where it is filtered out of the blood circulation and is concentrated in the urine
04142023 20
Detoxification
The liver detoxifies alcohol and drugs Toxins can also be rendered harmless by oxidation reduction methylation or a combination with another molecule
Liver cells contain many enzymes that enable rendering of toxic molecules less toxic form
This includes catalase which converts H2O2 to oxygen and water
DETOXIFICATION OF ALCOHOL
Alcohol is a CNS depressant contains a lot of energy that can be used for respiration STEP 1 Ethanol Ethanol dehydrogenase Ethanal (occurs in the hepatocytes)
The hydrogens release in the steps above are combined with NAD NADH
NAD is required to oxidise and breakdown fatty acids for use in respiration
04142023 21
Future Possible Complications
If the liver has to detoxify too much alcohol it has insufficient NAD to deal with the fatty acids
These fatty acids are converted back to lipids and are stored in the hepatocytes causing the liver to become enlarged
Causes a condition known as fatty liver alcohol-related hepatitis or cirrhosis
04142023 22
Stretching Your KnowledgeScenario
Liver cells contain a large group of enzymes called the cytochrome P450 enzymes These are responsible for the breakdown of some toxic molecules such as cocaine and other drugs (recreational and medicinal) The P450s are most concentrated in the endoplasmic reticulum of liver cells As a result of variation these enzymes can be more effective in some people than in others (Caucasian population compared to Afro-Caribean population)
Many drugs can be more effective in some people than in others and may also cause variable side effects
Task
1 Suggest why the P450s are most concentrated in the endoplasmic reticulum
2 Suggest why many medicinal drugs have different side effects in different people
3 Explain why the P450s are not identical in every person
The P450s are proteins these are manufactured by the ribosomes that are attached to the endoplasmic reticulum ndash they can be packaged in vesicles and transported to where they are needed
Each person may have slightly different enzymes (evolution) These may break the drugs down in a slightly different way producing different by-products (SEs)
Genetic variation means that different people will have different alleles ndash these will produce slightly different enzymes
04142023 23
Questions
1 Why must ammonia be converted to urea
2 Explain why excess amino acids and alcohol should not be excreted
3 Suggest why the liver cells have large number of mitochondria and ribosomes
Ammonia is highly soluble and very toxic urea is less soluble and less toxic
They contain valuable energy that can be converted to useable forms Some amino acids can be converted into other amino acids
The mitochondria provide ATP (metabolic energy) for the active or energy-requiring processes eg protein synthesis mitosis active transport endo and exocytosis The ribosomes manufacture the many enzymes that are needed in liver cells
04142023 24
124 The Kidney
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 19
Formation of Urea DEAMINATION
Removal of NH3 group fro the amino acid with oxygen forming a keto acid (-RCOCOOH) and Ammonia (NH3)
Ammonia is highly toxic and very soluble therefore should not be allowed to accumulate in the blood circulation
On removal of NH3 group energy is released
THE ORNITHINE CYCLE
Ammonia is converted into a less soluble and less toxic substance when combined with CO2 forming Urea
Urea is further passed into the blood circulation and into the kidneys where it is filtered out of the blood circulation and is concentrated in the urine
04142023 20
Detoxification
The liver detoxifies alcohol and drugs Toxins can also be rendered harmless by oxidation reduction methylation or a combination with another molecule
Liver cells contain many enzymes that enable rendering of toxic molecules less toxic form
This includes catalase which converts H2O2 to oxygen and water
DETOXIFICATION OF ALCOHOL
Alcohol is a CNS depressant contains a lot of energy that can be used for respiration STEP 1 Ethanol Ethanol dehydrogenase Ethanal (occurs in the hepatocytes)
The hydrogens release in the steps above are combined with NAD NADH
NAD is required to oxidise and breakdown fatty acids for use in respiration
04142023 21
Future Possible Complications
If the liver has to detoxify too much alcohol it has insufficient NAD to deal with the fatty acids
These fatty acids are converted back to lipids and are stored in the hepatocytes causing the liver to become enlarged
Causes a condition known as fatty liver alcohol-related hepatitis or cirrhosis
04142023 22
Stretching Your KnowledgeScenario
Liver cells contain a large group of enzymes called the cytochrome P450 enzymes These are responsible for the breakdown of some toxic molecules such as cocaine and other drugs (recreational and medicinal) The P450s are most concentrated in the endoplasmic reticulum of liver cells As a result of variation these enzymes can be more effective in some people than in others (Caucasian population compared to Afro-Caribean population)
Many drugs can be more effective in some people than in others and may also cause variable side effects
Task
1 Suggest why the P450s are most concentrated in the endoplasmic reticulum
2 Suggest why many medicinal drugs have different side effects in different people
3 Explain why the P450s are not identical in every person
The P450s are proteins these are manufactured by the ribosomes that are attached to the endoplasmic reticulum ndash they can be packaged in vesicles and transported to where they are needed
Each person may have slightly different enzymes (evolution) These may break the drugs down in a slightly different way producing different by-products (SEs)
Genetic variation means that different people will have different alleles ndash these will produce slightly different enzymes
04142023 23
Questions
1 Why must ammonia be converted to urea
2 Explain why excess amino acids and alcohol should not be excreted
3 Suggest why the liver cells have large number of mitochondria and ribosomes
Ammonia is highly soluble and very toxic urea is less soluble and less toxic
They contain valuable energy that can be converted to useable forms Some amino acids can be converted into other amino acids
The mitochondria provide ATP (metabolic energy) for the active or energy-requiring processes eg protein synthesis mitosis active transport endo and exocytosis The ribosomes manufacture the many enzymes that are needed in liver cells
04142023 24
124 The Kidney
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 20
Detoxification
The liver detoxifies alcohol and drugs Toxins can also be rendered harmless by oxidation reduction methylation or a combination with another molecule
Liver cells contain many enzymes that enable rendering of toxic molecules less toxic form
This includes catalase which converts H2O2 to oxygen and water
DETOXIFICATION OF ALCOHOL
Alcohol is a CNS depressant contains a lot of energy that can be used for respiration STEP 1 Ethanol Ethanol dehydrogenase Ethanal (occurs in the hepatocytes)
The hydrogens release in the steps above are combined with NAD NADH
NAD is required to oxidise and breakdown fatty acids for use in respiration
04142023 21
Future Possible Complications
If the liver has to detoxify too much alcohol it has insufficient NAD to deal with the fatty acids
These fatty acids are converted back to lipids and are stored in the hepatocytes causing the liver to become enlarged
Causes a condition known as fatty liver alcohol-related hepatitis or cirrhosis
04142023 22
Stretching Your KnowledgeScenario
Liver cells contain a large group of enzymes called the cytochrome P450 enzymes These are responsible for the breakdown of some toxic molecules such as cocaine and other drugs (recreational and medicinal) The P450s are most concentrated in the endoplasmic reticulum of liver cells As a result of variation these enzymes can be more effective in some people than in others (Caucasian population compared to Afro-Caribean population)
Many drugs can be more effective in some people than in others and may also cause variable side effects
Task
1 Suggest why the P450s are most concentrated in the endoplasmic reticulum
2 Suggest why many medicinal drugs have different side effects in different people
3 Explain why the P450s are not identical in every person
The P450s are proteins these are manufactured by the ribosomes that are attached to the endoplasmic reticulum ndash they can be packaged in vesicles and transported to where they are needed
Each person may have slightly different enzymes (evolution) These may break the drugs down in a slightly different way producing different by-products (SEs)
Genetic variation means that different people will have different alleles ndash these will produce slightly different enzymes
04142023 23
Questions
1 Why must ammonia be converted to urea
2 Explain why excess amino acids and alcohol should not be excreted
3 Suggest why the liver cells have large number of mitochondria and ribosomes
Ammonia is highly soluble and very toxic urea is less soluble and less toxic
They contain valuable energy that can be converted to useable forms Some amino acids can be converted into other amino acids
The mitochondria provide ATP (metabolic energy) for the active or energy-requiring processes eg protein synthesis mitosis active transport endo and exocytosis The ribosomes manufacture the many enzymes that are needed in liver cells
04142023 24
124 The Kidney
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 21
Future Possible Complications
If the liver has to detoxify too much alcohol it has insufficient NAD to deal with the fatty acids
These fatty acids are converted back to lipids and are stored in the hepatocytes causing the liver to become enlarged
Causes a condition known as fatty liver alcohol-related hepatitis or cirrhosis
04142023 22
Stretching Your KnowledgeScenario
Liver cells contain a large group of enzymes called the cytochrome P450 enzymes These are responsible for the breakdown of some toxic molecules such as cocaine and other drugs (recreational and medicinal) The P450s are most concentrated in the endoplasmic reticulum of liver cells As a result of variation these enzymes can be more effective in some people than in others (Caucasian population compared to Afro-Caribean population)
Many drugs can be more effective in some people than in others and may also cause variable side effects
Task
1 Suggest why the P450s are most concentrated in the endoplasmic reticulum
2 Suggest why many medicinal drugs have different side effects in different people
3 Explain why the P450s are not identical in every person
The P450s are proteins these are manufactured by the ribosomes that are attached to the endoplasmic reticulum ndash they can be packaged in vesicles and transported to where they are needed
Each person may have slightly different enzymes (evolution) These may break the drugs down in a slightly different way producing different by-products (SEs)
Genetic variation means that different people will have different alleles ndash these will produce slightly different enzymes
04142023 23
Questions
1 Why must ammonia be converted to urea
2 Explain why excess amino acids and alcohol should not be excreted
3 Suggest why the liver cells have large number of mitochondria and ribosomes
Ammonia is highly soluble and very toxic urea is less soluble and less toxic
They contain valuable energy that can be converted to useable forms Some amino acids can be converted into other amino acids
The mitochondria provide ATP (metabolic energy) for the active or energy-requiring processes eg protein synthesis mitosis active transport endo and exocytosis The ribosomes manufacture the many enzymes that are needed in liver cells
04142023 24
124 The Kidney
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 22
Stretching Your KnowledgeScenario
Liver cells contain a large group of enzymes called the cytochrome P450 enzymes These are responsible for the breakdown of some toxic molecules such as cocaine and other drugs (recreational and medicinal) The P450s are most concentrated in the endoplasmic reticulum of liver cells As a result of variation these enzymes can be more effective in some people than in others (Caucasian population compared to Afro-Caribean population)
Many drugs can be more effective in some people than in others and may also cause variable side effects
Task
1 Suggest why the P450s are most concentrated in the endoplasmic reticulum
2 Suggest why many medicinal drugs have different side effects in different people
3 Explain why the P450s are not identical in every person
The P450s are proteins these are manufactured by the ribosomes that are attached to the endoplasmic reticulum ndash they can be packaged in vesicles and transported to where they are needed
Each person may have slightly different enzymes (evolution) These may break the drugs down in a slightly different way producing different by-products (SEs)
Genetic variation means that different people will have different alleles ndash these will produce slightly different enzymes
04142023 23
Questions
1 Why must ammonia be converted to urea
2 Explain why excess amino acids and alcohol should not be excreted
3 Suggest why the liver cells have large number of mitochondria and ribosomes
Ammonia is highly soluble and very toxic urea is less soluble and less toxic
They contain valuable energy that can be converted to useable forms Some amino acids can be converted into other amino acids
The mitochondria provide ATP (metabolic energy) for the active or energy-requiring processes eg protein synthesis mitosis active transport endo and exocytosis The ribosomes manufacture the many enzymes that are needed in liver cells
04142023 24
124 The Kidney
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 23
Questions
1 Why must ammonia be converted to urea
2 Explain why excess amino acids and alcohol should not be excreted
3 Suggest why the liver cells have large number of mitochondria and ribosomes
Ammonia is highly soluble and very toxic urea is less soluble and less toxic
They contain valuable energy that can be converted to useable forms Some amino acids can be converted into other amino acids
The mitochondria provide ATP (metabolic energy) for the active or energy-requiring processes eg protein synthesis mitosis active transport endo and exocytosis The ribosomes manufacture the many enzymes that are needed in liver cells
04142023 24
124 The Kidney
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The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 24
124 The Kidney
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 25
The structure of the kidney
Positioned at each side of the spine just below the lowest rib
Supplied with blood from a renal artery and is drained by a renal vein
JOB - remove waste products from the blood and to produce urine
Urine passes out of the kidney down the ureter to the bladder where it can be stored before release
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 26
The Nephron- Part I
The bulk of each kidney consists of tiny tubules called nephrons
They are closely associated with tiny blood capillaries
Each nephron starts in the cortex In the cortex the capillaries form
a knot called the glomerulus
This is surrounded by a cup-shaped structure called the Bowmanrsquos Capsule
Fluid from the blood is pushed into the Bowmanrsquos capsule by the process of ultrafiltration
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 27
The Nephron- Part II
The capsule leads into the nephron which is divided into 4 parts
The proximal convoluted tubule
Loop of Henle (Descending and Ascending Limb)
Distal convoluted tubule
Collecting duct
As fluid moves along the nephron its composition is altered This is achieved by selective reabsorption Substances are reabsorbed back into the tissue fluid and blood capillaries surrounding the nephron tubule
The final product in the collecting duct is urine passed into the pelvis ureter bladder
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 28
How does the composition of the fluid change
In the PCT the fluid is altered by the reabsorption of all the sugars most salts and some water
In total about 85 of the fluid is reabsorbed here
In the DL of the Loop of Henle the water potential of the fluid is decreased by the addition of salts and removal of water
In the AL of the Loop of Henle the water potential of the fluid is increased as salts are removed by active transport
In the collecting duct the water potential is decreased again by the removal of water
This ensures that the final product (urine) has a low water potential
Urine has a higher concentration of solutes than is found in the blood and tissue fluid
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 29
Questions
1 Suggest why the nephrons are convoluted
2 Why are there many capillaries around each nephron
3 Explain why reabsorption from the nephron must be selective
The fact that the nephrons are convoluted allows there to be an increase the length for greater surface area for absorption or filtration This ensures accuracy and minimizes loss in terms of absorption of useful molecules required for the body
Materials reabsorbed from the fluid in the tubule can re-enter the blood circulation
Some of the molecules in the nephron are waste and must be left in the fluid to be excreted Other molecules are useful to the body and must be reabsorbed
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 30
Practice Exam Questions
1 What is meant by the term excretion [2 marks]
2 Name the two excretory products produced in mammals [2 marks]
3 Name the two organs that remove these products from the body [2 marks]
4 Name the blood vessels that carry blood to the liver [2 marks]
5 What is a sinusoid and where is it found [2 marks]
6 What is a hepatocyte [1 marks]
7 What is meant by the term deamination [2 marks]
8 What occurs during the ornithine cycle [2 marks]
9 Name the three sections of the kidney as seen in longitudinal section [3 marks]
10 Name the tubules found in the kidney [2 marks]
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 31
Practice Exam QuestionANSWERS
1 The removal of waste products from cell metabolism
2 Carbon dioxide and urea
3 The lungs and the kidneys
4 The hepatic artery( oxygenated blood) and hepatic portal vein (deoxygenated blood)
5 A sinusoid is a channel between the liver cells they are found in the liver lobules
6 A liver cell
7 The removal of the amino group from an amino acid forming ammonia and leaving a ketose residue
8 The conversion of ammonia to urea by the addition of carbon dioxide
9 Cortex medulla and pelvis
10 Nephrons
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 32
125 ndash Formation of Urine
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 33
Overview Videos
httpswwwyoutubecomwatchv=wWsdcfGta4k
httpswwwyoutubecomwatchv=Vqce2dtg45U
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 34
Ultrafiltration - PART I
Blood flows through the afferent arteriole into the glomerulus and blood leaves through the efferent arteriole
Afferent arteriole is wider in diameter than the efferent arteriole
Efferent arteriole is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries away blood away
This difference ensures the glomerulus is higher in pressure in comparison to the pressure in the Bowmanrsquos capsule
This pressure differences pushes the fluid from the blood into the Bowmanrsquos capsule
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 35
Ultrafiltration - PART II
The barrier between the blood in the capillary and the lumen of the Bowmanrsquos capsule consists of three layers
Endothelium of the capillary
A basement membrane
The epithelial cells of the Bowmanrsquos capsule (podocytes)
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 36
Ultrafiltration - PART III
Each structure is adapted to allow ultrafiltration
Fenestrated Endothelium ndash narrow gaps between each endothelium cells ndash blood plasma and substances dissolved in blood plasma can pass through these narrow gaps
Basement membrane ndash fine mesh of collagen fibres and glycoprotein
This filter prevent the passage of molecules with a relatively high molecular mass All proteins (and all blood cells) are held in the capillaries of the glomerulus
Epithelial cells of the Bowmanrsquos capsule are called PODOCYTES which have a specialized shape
Podocytes have finger-like projections called major processes Ensuring that gaps are present in between cells
The fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowmanrsquos capsule
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 37
What is filtered out of the blood
Blood plasma containing dissolved substances is pushed under pressure from the capillary into the lumen of the Bowmans capsule This includes the following substances
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+ Cl- K+)
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 38
What is left in the capillary
The blood cells and proteins are left in the capillary
Presence of the proteins means that the blood has a very low (very negative) water potential
Due to this low water potential it ensures that some of the fluid is retained in the blood and this contains some of the water and dissolved substances listed above
The very low water potential of the blood in the capillaries is important to help reabsorb water at a later stage
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 39
Stretching Your KnowledgeScenario
High Blood pressure can damage the capillaries of the glomerulus and the epithelium of Bowmanrsquos capsule
Task
Explain why the presence of protein in urine can be a sign of hypertensionProteins are normally filtered by the basement membrane If this has been damaged by high blood pressure then proteins can enter bowmans capsule from the blood and pass into the urine presenting as proteinuria
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 40
Selective Reabsorption- PART I
Reabsorption is achieved by a combination of processes described below The cells lining the proximal convoluted tubule are specialized to achieve this reabsorption
PCT cells are highly folded forming microvilli for increase surface area for reabsorption
PCT cells also have special co-transporter proteins transporting glucose or amino acids in association with sodium ions from the tubule into the cell facilitated diffusion
Molecules are moving from a high water potential to a low water potential (no ATP is required)
PCT cells lined towards the capillaries are also highly folded forming microvilli for increased surface area This membrane contains sodium-potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
These pumps require ATP so have high amounts of mitochondria surrounding
Large molecules such as small proteins that may have entered the tubule will be reabsorbed by endocytosis
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 41
Selective Reabsorption- PART I
PCT cells lining towards the capillaries
PCT cells lining
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 42
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 43
Questions
1 Explain what is meant by ultrafiltration
2 Suggest what might happen if water is not reabsorbed from the nephron
3 Explain why the concentrations of glucose and amino acids are the same in the glomerular filtrate as in the blood plasma
Filtering on a molecular scale Small molecules pass through the basement membrane which acts as a filter while larger molecules are held in the blood
A large volume of very dilute urine would be produced and dehydration would occur
Because the amino acids and glucose have been passed from the blood plasma to the glomerular filtrate by ultrafiltration in the glomerulus
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 44
126 ndash Water reabsorption
OCR ndash A2 ndash Module 2
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 45
Reabsorption of Water
Each minute 125cm3 of fluid is filtered from the blood and enters the nephron tubules
After selective reabsorption in the proximal convoluted tubules about 45cm3 is left
The role of the loop of henle is to create a low (very negative) water potential in the tissue of the medulla ensures that more water can be reabsorbed from the fluid in the collecting duct
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 46
The Loop of Henle - Part I
Consists of a descending limb which descends into the medulla and an ascending limb that ascends back out to the cortex
The overall effect of the loop of henle
Filter the fluid entering the descending limb which is slightly concentrated
Osmotically removing water from the descending limb into the Vasa Recta
Water potential decreases and is highly concentrated as you enter the ascending limb
Here Na+ and Cl- ions are actively removed from the ascending limb into the Vasa Recta
The ascending limb is impermeable to water so cannot leave the tubule
The ascending limb increases in water potential as it enters the DCT
= COUNTERCURRENT MULTIPLIER
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 47
The Loop of Henle - Part II
Vasa Recta surrounds the loop of henle in an opposing fashion
As you go down the descending limb in the loop of henle you are ascending in the Vasa Recta as you go up the ascending limb in the loop of henle you are descending in the Vasa Recta
The top of the ascending limb urine is highly dilute (watery) therefore as you continue from the DCT and CT water is reabsorbed leaving a concentrated fluid which is excreted
The amount of water reabsorbed depends on the needs of the body and so the kidney is also an organ of osmoregulation
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 48
The Collecting Duct
At the top of the ascending limb it connects to the DCT which is very short in comparison to your PCT active transport is used to reabsorb water from your DCT into your surrounding tissue fluid
From the DCT CD water has a high water potential therefore the CD carries on removing water leaving as it descends from the medulla into your pelvis
The remaining solute left becomes highly concentrated and is excreted
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 49
Stretching Your KnowledgeScenario
Question Why do camels have humps Answer It was a myth that the hump was due to a long loop of henle However current research shows that the hump stores fat which can be metabolized to release energy and water But why do camels need an extra long loop of Henle All mammals adapted to living in arid regions share this feature It provides them with a longer countercurrent mechanism that can increase the salt concentration in the medulla more than in other mammals
Task
Explain why it is beneficial to mammals living in arid regions to have higher salt concentrations in their medullas A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 50
Stretching Your KnowledgeScenario
The tissue fluid in the medulla has a low water potential so how can water pass from the tissue fluid into the blood plasma by osmosis
Task
Explain an arrangement of the blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
A higher salt concentration in the medulla means that a greater water potential gradient can be achieved between the urine in the CD and the medulla This means that more water can be reabsorbed from the CD and then pass into blood capillaries and the urine is made more concentrated There will be less urine produced and less water lost
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 51
Questions
1 Why must the collecting duct pass back through a region of low water potential
2 Why is it important for terrestrial mammals to reabsorb as much water as possible
3 Suggest why beavers have short loops of Henle
This arrangement allow water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla This concentrates the urine
Terrestrial mammals gain water by eating and drinking They lose water through sweat exhaling excretion and egestion It is important not to lose more water than necessary as it may not be readily available
Beavers live beside or in water Water is readily available and they do not need to conserve it as much
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 52
127 - Osmoregulation
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 53
Osmoregulation
Osmoregulation = control of water levels and salt levels in the body Water is gained from Food drink metabolism
Water is lost in urine sweat water vapor in exhaled air faeces
When drinking plentiful fluid you will produce a large volume of dilute urine
When drinking a less amount of fluid you will produce smaller volumes of more concentrated urine
The walls of the collecting duct can be made more or less permeable according to the needs of the body
On a cool day your requirement of water is lower therefore the walls of the collecting duct are less permeable and less water is reabsorbed therefore producing more urine
On a warmer day you requirement of water is much more greater therefore the walls of the collecting duct are more permeable and more water is reabsorbed therefore producing a smaller volume of urine
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 54
Altering the permeability of the CD- PART I
The walls of the collecting duct respond to Antidiuretic hormone (ADH) in the blood
ADH has an antidiuretic action that prevents the production of dilute urine (and so is called an antidiuretic)
Cells in the wall have membrane-bound receptors for ADH
The ADH binds to these receptors and causes a chain of enzyme-controlled reactions inside the cell
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 55
Altering the permeability of the CD- PART II
If there is more ADH in the blood then vesicles containing water-permeable channels (aquaporins) will fuse into the cell surface membrane
Therefore the walls more permeable to water More ADH = More permeable channels inserted more water reabsorbed by osmosis More concentrated urine
If there is less ADH in the blood then the cell surface membrane folds inwards to create new vesicles that remove water-permeable channels from the membrane
Therefore the walls less permeable to water less water is reabsorbed via osmosis into the blood more water passes out into the (dilute) urine
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 56
Normal Effect
>
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
57
Too Much Water
>
QuickCast|744|416
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 58
Too Little Water
>
QuickCast|744|417
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 59
Adjusting the concn of ADH in the blood- PART I
The Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain
When water potential of the blood is low the osmoreceptor cells lose water by osmosis causing them to shrink stimulates neurosecretory cells in the hypothalamus
The neurosecretory cells are specialized neurons (nerve cells) that produce and release ADH
ADH releasing cell bodies are found to lie in the hypothalamus
ADH flows down the axon to the terminal bulb in the posterior pituitary gland and stored until needed
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 60
Adjusting the concn of ADH in the blood- PART II
When the neurosecretory cells are stimulated they send an AP down their axons and cause the release of ADH
ADH enters blood capillaries running through the posterior pituitary gland around the body acts on the cells of the collecting ducts
Once water potential rises less ADH is released
ADH is slowly broken down and collecting ducts will receive less stimulation ndash half-life of about 20minutes
Half-life of a substance is the time taken for itrsquos concentration to drop to half itrsquos original value
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 61
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 62
Control of water potential in the blood by negative feedback
Increase in water potential of blood
Detected by osmoreceptors in hypothalamus
Less ADH released from the posterior hypothalamus
Collecting duct walls less permeable
Less water reabsorbed into blood more urine produced
Decrease in water potential of blood
Normal water potential of blood
Decrease in water potential of blood
Detected by osmoreceptors in hypothalamus
More ADH released from the posterior hypothalamus
Collecting duct walls more permeable
More water reabsorbed into blood less urine produced
Decrease in water potential of blood
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
63
Stretching Your KnowledgeScenario
A number of drugs have an effect on urine production Some have effects that are unwanted or may be a nuisance Alcohol inhibits the production of ADH and certain antibiotics such as tetracycline can cause renal failure through a variety of mechanisms including direct toxicity to the nephron tubules
Other drugs have effects that may be useful Diuretic drugs increase urine production and antidiuretic drugs do the opposite by increasing the reabsorption of water at the distal tubule and collecting ducts without significantly modifying the rate of glomerular filtration
Task
Explain why drinking too much alcohol can cause a hangover
Suggest what symptoms may be relieved by the use of (i) Diuretics and (ii) antidiuretics
Alcohol inhibits the release of ADH therefore the collecting ducts are not very permeable and less water is reabsorbed This means that more water is lost in urine and dehydration occurs The ethanal produced form the metabolism of ethanol also contributes to the headache
(i) ndash Diuretic drugs can be used to relieve water retention which can cause swelling and high blood pressure
(ii) Antidiuretic drugs can be used to relieve diabetes insipidus (a form of diabetes caused by a lack of ADH resulting in very large amounts of watery urine) and bed wetting
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 64
Questions
1 How do neurosecretory cells differ from normal nerve cells
2 Explain what is meant by negative feedback
3 Why is it important that ADH is broken down
Neurosecretory cells manufacture a hormone in their cell body this is transferred down the axon When it is released it goes straight into the blood rather than to another nerve cell
Negative feedback occurs when a change in the internal conditions stimulates a reversal of that change ndash so the conditions are kept constant
ADH must be broken down so that it is not continually acting on the walls of the collecting ducts
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 65
128 ndash Kidney Failure
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 66
Kidney Failure
Most common causes are
Diabetes mellitus (both type I and type II sugar diabetes)
Hypertension
Infection
Once the kidneys fail completely the body is unable to remove excess water and certain waste products from the blood
This includes urea and excess salts
It is also unable to regulate the levels of water and salts in the body rapid death
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 67
Treatment of Kidney Failure- PART I
Two main treatments for CKD
Dialysis (2 subtypes)
most common treatment removing waste excess fluid from blood by passing the blood over a dialysis membrane The membrane is a partially permeable membrane that allows the exchange of substances between the blood and dialysis fluid
This fluid contains the correct concentrations of salts urea water and other substances in blood plasma
Any substances in excess in the blood diffuse across the membrane into the dialysis fluid
Any substances that are too low in concentration diffuse into the blood from the dialysis fluid
Dialysis must be combined with a carefully monitored diet
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 68
Treatment of Kidney Failure- PART II
Hemodialysis
Blood from a vein is passed into a machine that contains an artificial dialysis membrane Heparin is added to avoid blood clotting and any bubbles are removed before the blood returns to the body
Hemodialysis is usually performed at a clinic 3 times a week for several hours at each sessions but some patients learn to carry it out at home
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 69
Treatment of Kidney Failure- PART III
Peritoneal Dialysis
The filter is the bodyrsquos own abdominal membrane (peritoneum)
First a surgeon implants a permanent tube in the abdomen
Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs
After several hours the used solution is drained from the abdomen
PD is usually performed in several consecutive sessions daily at home or work
As the patient can walk around having dialysis the method is sometimes called ambulatory PD
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 70
Treatment of Kidney Failure- PART IV
Kidney Transplant In a kidney transplant the old kidneys are left in place unless they are likely to
cause infection or are cancerous The donor kidney can be from a living relative who is willing to donate one of their healthy kidneys or from someone who has died
A kidney transplant is major surgery While the patient is under anesthesia the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and the bladder
Many patients feel much better immediately after the transplant which is the best life-extending treatment for kidney failure
However the patientrsquos immune system will recognize the new organ as a foreign object and produce a reaction
Patients are given immunosuppressant drugs to help prevent rejection
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 71
Advantages and Disadvantages of Kidney Transplant
Advantages Disadvantages
Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney
Diet is less limited Need major surgery under a general anesthetic
Feeling better physically Risks of surgery include infection bleeding and damage to surrounding organs
A better quality of life ie able to travel Frequent checks for signs of organ rejection
No longer seeing oneself as chronically ill Side effects anti-rejection medicines cause fluid retention and high blood
pressure immunosuppressants increase susceptibility to infections
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 72
Testing Urine Samples- PART I
Substances or molecules with a relative molecular mass of less than 69000 can enter the nephron This means that any metabolic product or other substance that is in the blood can be passed into the urine ndash as long as it is small enough
If these substances are not reabsorbed further down the nephron they can be detected in urine
Pregnancy Testing
Once implanted in the uterine lining a human embryo starts secreting a pregnancy hormone called human chorionic gonadotrophins (hCG) (Mr = 36700)
It can be found in urine as early as 6 days after conception The pregnancy tests on the market today are manufactured with monoclonal antibodies
Antibody is specific it will only bind to hCG not to other hormones
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 73
Testing Urine Samples- PART II
When someone takes a home pregnancy test she soaks a portion of the test strip in her urine
Any hCG in the urine attaches to an antibody that is tagged with a blue bead
This hCG-antibody complex moves up the strip until it sticks to a band of immobilized antibodies
As a result all the antibodies carrying a blue bead and attached to hCG are held in one place forming a blue line
There is always one control blue line to use for comparison a second blue line indicates pregnancy
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
74
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 75
Testing Urine Samples- PART III
Testing for anabolic steroids
Anabolic Steroids ndash increase protein synthesis within cells build-up of cell tissues especially in the muscles
Non-medical uses for anabolic steroids are controversial because they can give advantage in competitive sports and they have dangerous side effects (use in sports is now banned)
Half-life of about 16 hours and remain in the blood for many days
Relatively small molecules and enter the nephron easily
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 76
Testing Urine Samples- PART IV
Testing for anabolic steroids involves analyzing a urine sample in a laboratory using gas chromatography or mass spectrometry
In a gas chromatography the sample is vaporized in the presence of a gaseous solvent and passed down a long tube lined by the absorption agent
Each substances dissolves differently in the gas and stays there for a unique specific time the retention time
Eventually the substances comes out of the gas and is absorbed onto the lining detector creates a chromatogram
Standard samples of drugs as well as the urine samples are run so that the drugs can be identified and quantified in the chromatograms
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 77
Questions
1 What components of the diet must be carefully monitored in someone who undergoes dialysis
2 Explain why hemodialysis fluid has to be sterile and at 37oC
3 Create a table of advantages and disadvantages of dialysis as a treatment for kidney failure
4 Explain why standard samples of drugs must be run alongside a urine sample in gas chromatography
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 78
Module Summary
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 79
Module Summary
121 ndash Excretion
Key Definitions
Excretion removal of metabolic waste form the body
Metabolic waste consists of waste substances that may be toxic or are produced in excess by the reactions inside cells
Deamination removal of an amine group from an amino acid to produce ammonia
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 80
Module Summary
122 ndash The Liver
Key Definitions
Hepatic Portal Vein unusual blood vessel that has capillaries at both ends ndash it carries blood from the digestive system to the liver
Function of Kupffer cells appears to be the breakdown and recycling of old red blood cells Bilirubin is ne of the waste products from the breakdown of hemoglobin
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 81
Module Summary
123 ndash Functions of the Liver
Key Definitions
Urea excretory product formed from the breakdown of excess amino acids
Ornithine cycle the process in which ammonia is converted to urea It occurs partly in the cytosol and partly in the mitochondria as ATP is used
Detoxification ndash conversion of toxic molecules to less toxic or non-toxic molecules
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 82
Module Summary
124 ndash The Kidney
Key Definitions
Nephron the functional unit of the kidney Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine which drains into the ureter
Glomerulus fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood It is surrounded by a cup-or funnel-shaped capsule which collects the fluid and leads into the nephron
In selective reabsorption useful substances are reabsorbed form the nephron into the bloodstream while other excretory substances remain in the nephron
The PCT is the closest to the Glomerulus The DCT is the furthest from the glomerulus
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 83
Module Summary
125 ndash Formation of Urine All organs have afferent vessels ndash they bring blood into the organ Similarly efferent vessels carry
blood away from the organ In a glomerulus the efferent vessels is an arteriole ndash which is muscular and can constrict to raise the blood pressure in the glomerulus In most organs a venule carries blood away
Ultrafiltration is filtration at a molecular level ndash as in the glomerulus where large molecules and cells are left in the blood and smaller molecules pass into the Bowmanrsquos capsule
Podocytes are specialized cells that make up the lining of the Bowmanrsquos capsule
TIP the endothelium of the capillary and the epithelium of Bowmanrsquos capsule contains gaps or pores These two layers of cells do little to filter out larger molecules IT is the basement membrane that is actually involved in ultrafiltration
Key Definitions
Microvilli are microscopic folds of the cell surface membrane that increase the surface area of the cell
Co-transporter proteins are proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose
Facilitated diffusion is diffusion that is enhanced by the action of proteins in the cell membrane
Sodium-Potassium pumps are special proteins in the cell surface membrane that actively transports sodium and potassium ions against their concentration gradient
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 84
Module Summary
156 ndash Water reabsorption
Key definitions
A hairpin countercurrent multiplier is the arrangement of a tubule in a sharp hairpin so that one part of the tubules passes close to another part of the tubule with the fluid flowing in opposite directions This allows exchange between the contents and can be used to create a very high concentration of solutes
Osmoregulation is the control and regulation of water potential of the blood and body fluids In humans the kidney controls the water potential of the blood
The distal convoluted tubule is the coiled portion of the nephron between the loop of henle and the collecting duct
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 85
Module Summary
157 ndash Osmoregulation
Key definitions
Antidiuretic Hormone (ADH) is released from the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water
Osmoreceptor are receptor cells that monitor the water potential of the blood IF the blood has a low water potential then water is moved out of the osmoreceptor cells by osmosis causing them to shrink This causes stimulation of the neurosecretory cells
Hypothalamus is part of the brain that contains neurosecretory cells and various receptors that monitor the blood
Neurosecretory cells are specialized cells that act like nerve cells but release a hormone into the blood ADH is manufactured in the cell body and passes down the axon to be stored in the terminal bulb If an action potential passes down the axon then ADH is released from the terminal bulb
Posterior pituitary gland is the hind part of the pituitary gland which releases ADH
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 86
Module Summary
158 ndash Kidney Failure
Key Definitions
Human chorionic gonadotrophins (hCG) is a hormone released by human embryos itrsquos presence in the mothers urine confirms pregnancy
Monoclonal antibodies are identical because they have been produced by cells that are clones of the original cell
Anabolic steroids are drugs that mimic the action of steroid hormones that increase muscle growth
Gas chromatography is a technique used to separate substances in a gaseous state A Chromatogram is a chart produced when substances are separated by movement of a solvent along a permeable material such as paper or gel
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
Stretching Your Knowledge (5)
Questions (5)
128 ndash Kidney Failure
Kidney Failure
Treatment of Kidney Failure - PART I
Treatment of Kidney Failure - PART II
Treatment of Kidney Failure - PART III
Treatment of Kidney Failure - PART IV
Advantages and Disadvantages of Kidney Transplant
Testing Urine Samples - PART I
Testing Urine Samples - PART II
Slide 74
Testing Urine Samples - PART III
Testing Urine Samples - PART IV
Questions (6)
Module Summary
Module Summary (2)
Module Summary (3)
Module Summary
Module Summary (4)
Module Summary (5)
Module Summary (6)
Module Summary (7)
Module Summary (8)
Thank you feel free to ask for any help
04142023 87
Thank you feel free to ask for any help
By Piril Erel
A2 ndash Module 1 ndash Unit 2 - Excretion
121 Excretion
What is excretion
Where are these substances excreted
Why must these substances be remove Part I
Why must these substances be removed Part II
Why must these substances be removed Part III
Why must these substances be removed Part IV
122 The Liver
The structure of the liver
Blood flow to the liver
Blood flow from the liver
The arrangement of cells inside the liver
Liver Cells
Kupffer cells
123 ndash Functions of the liver
Wide Range of functions of the liver
Formation of Urea
Formation of Urea
Detoxification
Future Possible Complications
Stretching Your Knowledge
Questions
124 The Kidney
The structure of the kidney
The Nephron - Part I
The Nephron - Part II
How does the composition of the fluid change
Questions (2)
Practice Exam Questions
Practice Exam Question ANSWERS
125 ndash Formation of Urine
Overview Videos
Ultrafiltration - PART I
Ultrafiltration - PART II
Ultrafiltration - PART III
What is filtered out of the blood
What is left in the capillary
Stretching Your Knowledge (2)
Selective Reabsorption - PART I
Selective Reabsorption - PART I (2)
Slide 42
Questions (3)
126 ndash Water reabsorption
Reabsorption of Water
The Loop of Henle - Part I
The Loop of Henle - Part II
The Collecting Duct
Stretching Your Knowledge (3)
Stretching Your Knowledge (4)
Questions (4)
127 - Osmoregulation
Osmoregulation
Altering the permeability of the CD - PART I
Altering the permeability of the CD - PART II
Normal Effect
Too Much Water
Too Little Water
Adjusting the concn of ADH in the blood - PART I
Adjusting the concn of ADH in the blood - PART II
Slide 61
Control of water potential in the blood by negative feedback
