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Unit 23: The Continuation of Life
Chapter 23:
Removal of Materials from the Blood.
19/04/23 Mrs Smith Ch23 The Removal of Materials from Blood
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Higher Human Biology
19/04/23 Mrs Smith Ch22 The delivery of nutrients to cells
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Learning Intentions
To understand how the liver, lungs and
kidneys are involved in the removal of
materials from the blood.
Success Criteria1. Describe the role of the liver
in:I. Conservation of useful
substancesII. Detoxification of toxic
materialsIII. Removal of bilirubinIV. Production of urea
Removal of materials from the body
The circulatory system is vital for the removal of materials from the body. The main organs that help remove unwanted materials are:
The lungs The liver
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The kidney
Concentration of CO2 in blood plasma > Concentration CO2 in air
1. The Lungs. The LungsCarbon Dioxide is a waste product of respirationCO2 is transported to the lungs, via the blood plasma,
to be removed from the body in the form of bicarbonate ions (HCO-3).
As blood flows through the pulmonary system these bicarbonate ions combine with hydrogen ions (H+) to form carbonic acid (H2CO3). An enzyme then breaks the carbonic acid down into water and CO2:
• So CO2 diffuses out of the blood into the lungs down a concentration gradient. Breathing, which exhales air rich in CO2, maintains this gradient.
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Diffusion in the alveoli
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Excretion of carbon dioxideExcretion = the elimination of waste products of metabolism
e.g. • Removal of CO2 (waste product of respiration) at the lungs.• Release of bile pigment in bile.
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2. Role of LiverThe liver removes materials from the blood by: • Conservation of useful substances.
– e.g. glucose, plasma proteins• Detoxification of toxic materials which are potentially toxic.• Removal of bilirubin and its excretion as bile.• Production of urea.
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Liver maintains a stable internal environment, and provides cells
with optimum conditions
Liver: Conservation of useful substances
Glucose Level regulated
• excess stored as glycogen which can be converted to glucose as
needed.
3 types of Plasma proteinsMaintains a stable
pool • some undergo
deamination in the liver
• meanwhile new molecules are synthesised
Components of blood plasma Regulated
• Stable internal environment maintained
• living cells have optimum conditions for growth & development
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Detoxification of toxic materials
• Certain substances which gain access to or are produced by the body as a result of metabolic reactions are potentially toxuc.
• They would do the body harm if left unaltered.
• These substances are detoxified by liver cells.
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Detoxification occurs in one of 4 ways
• Substances are detoxified by liver cells in one of 4 ways…..A. Chemical Alteration
B. Chemical Breakdown
C. Chemical attachment (conjugation).
D. Uptake by macrophages
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A. Chemical alteration
• Biologically active molecules (e.g. Drugs) are rendered inactive by being chemically altered in the liver.
• The products are then excreted in bile or released into the bloodstream and removed by the kidneys.
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Hydrogen peroxide, a highly toxic by-product of metabolism is broken down by the enzyme catalase into harmless substances.
Liver cells are rich in catalase.
B. Chemical breakdown
2H2O2 O22H2O+catalase
TOXIC Harmless
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• Alcohol (ethanol) gets converted in the liver, by a series of enzyme –controlled steps to acetyl CoA, which acts as a respiratory substrate for aerobic respiration.
• Too much alcohol damages cells. Regular consumption of alcohol to excess can cause permanent liver damage leading to a fatal liver condition called cirrhosis.
B. Chemical breakdown
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C. Chemical attachement
• Some unwanted substances (e.g. Certain types of food preservative) become attached to liver cells to the amino acid glycerine.
• This acts as a molecular label which is recognised as waste by the kidneys and excreted.
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D. Uptake by macrophages
• Foreign particles are removed by macrophages (phagocytic cells) which line the liver’s blood vessels.
• If for example an animal is injected intravenously with a suspension of carbon particles, samples of liver obtained only minutes later show numerous carbon-laden macrophage cells.
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Toxic substances, that have either been eaten or produced in metabolic reactions, must be destroyed to prevent them harming the body. Liver cells detoxify such substances.
Detoxification by liver cells
Liver: Detoxification of Materials: SUMMARY
Chemical breakdown
(see next page)
Products excreted in bile or released into blood and removed
by kidneys
Chemical alteration Biologically active
molecules altered in the liver.
Chemical attachment (conjugation)
Unwanted substance become attached by liver cells to the
amino acid glycine.
This acts as a chemical label which is recognised as a waste by the kidneys
and excreted
Uptake by macrophagesMacrophages line the liver’s blood vessels
removing foreign
particles
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19/04/23 Mrs Smith Ch22 The delivery of nutrients to cells
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Learning Intentions
To understand how the liver, lungs and kidneys are involved in the removal of materials from the blood.
Success Criteria1. 3. Describe the role of the
liver in:I. Conservation of useful
substancesII. Detoxification of toxic
materialsIII. Removal of bilirubinIV. Production of urea
3. Removal of bilirubinWhen red blood cells reach
the end of their 120 day life span, they are destroyed by macrophage cells in the liver, bone marrow and spleen,
Haemoglobin is broken down by theses cells into a yellow pigment called bilirubin. Biliruben is releases into the blood giving blood plasma its yellowish colour. 19/04/23
18Mrs Smith Ch23 The Removal of
Materials from Blood
Excretion of bilirubin
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Bilirubin molecules, removed from the blood plasma by the liver, are added to bile with the aid of enzymes and become bile pigment (Conjugated bilirubin). This has no useful role in digestion so is released in bile.
In the gut, bilirubin is converted by bacteria to the brown pigment that gives faeces its brown colour.
Bilirubin accumulates in the bloodstream when:
4. Jaundice
• Liver cells can’t absorb bilirubin (due to illness e.g. hepatitis).
• The bile duct becomes blocked preventing the release of bile to small intestine.
• Red blood cell destruction is excessively high.
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Jaundice is caused by excessively high concentrations of bilirubin.
4. Jaundice4. Jaundice
Baby’s can be screened for Bilirubin using a light meter that is placed on the baby’s head.
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Learning Intentions
To understand how the liver, lungs and kidneys are involved in the removal of materials from the blood.
Success Criteria
2. Determining the quantity of urea in urine samples
Production of Urea: Deamination
• Unlike carbohydrate and lipid, protein is not stored in the body. Excess amino acids are absorbed from the gut then undergo deamination in liver cells.
• De-amination needs oxygen• It produces an organic acid• It produces ammonia which
goes to the ornithine cycle.
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During this process, the amino acid is broken down to form ammonia and an organic acid.
5. Production of urea
Breakdown of amino acids
Organic acid(Kreb cycle
intermediate or pyruvic acid)
Ammonia
Used for energy
release in respiation
+ CO2
Very toxic
+ H2OUrea
Less toxic
Passes into blood and leaves the liver by the hepatic vein. It is
removed from the blood at the kidneys.
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Fate of deaminated amino acids
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• Depending on which amino acid has been deaminated the organic acid may be pyruvic acid or one of Krebs Cycle intermediates.
• It can then enter the respiratory pathway or be used for energy release.
Ornithine cycle
• Since ammonia is formed during deamination of an amino acid is highly toxic, it is immediately passed to the ornithine cycle.
• This cycle is controlled by enzymes in the liver cells.
• Here Ornithine is constantly regenerated.
• During this cycle , ammonia reacts with carbon dioxide to form less toxic urea and water.
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Urea production
• During the conversion of ammonia into urea, two molecules of ammonia and one molecule of carbon dioxide combine to form one molecule of urea and one of water. Assisting this process there is a cyclical conversion of ornithine into citrulline, arginine, and then back to ornithine again.
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Where does the urea go?
• Urea is then passed into the bloodstream and then leaves the liver by the hepatic vein.
• It is removed from blood by the kidneys.
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Determining the quantity of urea in Determining the quantity of urea in ‘urine’ samples‘urine’ samples
The combination of urea with water is catalysed by the enzyme urease:
+H2OUreaurease
ammonium carbonate(an alkali)
The quantity of urea in the original solution is directly related to the quantity of alkali produced. This can be determined by the volume of acid needed to neutralise the alkali.
Methyl orange, an indicator, is used to show the change from alkali (orange) to acid (red).
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Using urea solutions of known concentration a calibration graph can be drawn.
Using solutions of known concentration to plot a calibration graph
• Four solutions of know urea concentration are made up.• Following enzyme activity at 37oC, each solution is titrated
against hydrochloric acid.• The volume of hydrochloric acid needed to neutralise the
alkali in each solution is indicated by methyl orange changing colour.
• This is repeated for each conc many times and results are pooled and averaged.
• The results are then plotted to make a calibration graph.
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Urea Concentration Calibration Curve
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The following experiment is carried out on a sample of urine (urea concentration unknown) and compared to the calibration curve.
50 cm3 urea solution (urea +
water)
+ 2 crushed urease tablets
In water bath at 37oCfor 90 mins
Flasks shaken at
15min intervals
After 90 mins,
20 drops of methyl
orange added + 0.1M HCl
until indictor turns red
to increase surface area
to aid mixing of enzyme & substrate
Many repeats done to increase reliability of results.
Optimum temperature for enzyme activity
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Using a calibration graph to calculate the urea content of unknown samples
Task: Torrance-TYK pg178 Qu 1-3
19/04/23 33Mrs Smith Ch20: Transport Mechanisms - The Cardiac Cycle
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Learning Intentions
To understand how the liver, lungs and kidneys are involved in the removal of materials from the blood.
Success Criteria4. Label a diagram of a
kidney nephron
5. Explain the mechanism of kidney function to includeI. Ultrafiltration
6. Structure of the Kidney
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6.The Kidneys: Structure
Each kidney has about a million tiny filtering units called nephrons.
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Each nephron is composed of several part
The capillaries in the glomerulus are narrower than the capillary that supplied it with blood. What effect will this have on the blood pressure in the glomerulus?
Bowman's capsule
glomerulus
blood capillaries
collecting duct
nephron
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Nephrons• Each nephron is composed of several parts.• A glomerulus is enclosed in a cup-shaped Bowman’s
capsule which leads into a long kidney tubule surrounded by a dense network of blood capillaries.
• Two regions of the tubule possess several twists and turns and are therefore described as convoluted. The proximal convoluted tubule is the twisted region at the greater distance from the Bowman’s capsule.
• The long, U-shaped stretch of tubule between the convoluted regions is called the loop of Henle.
• Each kidney tubule leads to a communal collecting duct.
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The Kidney NephronThe Kidney NephronKnot of tiny blood
vessels
Loop of Henle
Bowman’s capsule
The blood enters the nephron via the renal artery and leaves via the renal vein. At the glomerulus the blood is filtered and the filtrate gathers in the bowman’s capsule. The filtrate then passes along the tubule to the communal collecting duct.
Has many twists &
turns
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The Kidneys: Function: Production of Urine
• The kidneys remove waste material from the blood and excrete them in urine.
• The production of urine involves the – ultrafiltration of blood
– reabsorption of useful materials from the filtrate.
• Since urine contains urea, a nitrogenous waste, the kidneys are described as organs of nitrogenous excretion.
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• Ultrafiltration happens at the Bowman’s capsule.
• Blood containing waste products enters the kidney by the renal artery which divides into about a million branches each supplying a glomerulus.
• Each glomerulus consists of a coiled knot of blood capillaries. This arrangement enables a large surface area of blood vessel to be in contact with the inner lining of the Bowman’s capsule.
• It is at this interface ultrafiltration takes place
7. Ultrafiltration
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Ultrafiltration- Basement membrane filter.
The layer of cells which makes up the capillary wall of a glomerulus differs from a normal capillary because.....
•It has pores which are large enough to let ALL the substances within plasma pass through.
•The porous layer is attached to a highly permeable thin layer of non-living material called the basement membrane.•The basement membrane has no pores but acts as a filter that...
– Allows small molecules such as glucose, water, salts & urea to pass through.
– Prevents large molecules of plasma protein from leaving the blood stream.
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glucose
ions
urea
water
protein
Protein molecules pass through the fenestrated endothelial layer of the
capillaries, but are prevented from passing
into the cavity of Bowman’s capsule by the basement
membrane
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Blood Pressure
• Plasma proteins which remain in the blood plasma tend to draw water back from the filtrate in the capsule by osmosis.
• In addition filtrate already present in the capsule tends to resist the delivery of further filtrate into the capsule.
• Successful ultrafiltration of blood depends on the blood in the glomeruli being at high enough pressure to overcome both of these factors and force filtrate out of the plasma.
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Did you know? An adult has ~ 4.5 l of blood,
but the kidneys filter ~ 1500 l of blood/day!
Ultrafiltration and Blood PressureUltrafiltration and Blood Pressure..• High blood pressure in the glomerulus is needed
to force the filtrate out of the blood plasma. This is maintained because:– The blood vessels leading to the glomerulus come
from the renal artery, which is a branch from the aorta so carries blood at high pressure
– The blood vessels entering the glomerulus are wider than the blood vessels leaving it, causing a bottle-neck and the blood to be squeezed
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Ultrafiltration – Rate of production of filtrate and urine.
• A human adult contains about 4.5 litres of blood.• During its continuous circulation round the body,
blood repeatedly enters the kidneys and undergoes filtration.
• Each day a human adult’s kidneys filter a total volume of around 1500 litres of blood and produce about 180 litres of glomerular filtrate.
• However the production of urine is only about 1-2 litres.
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19/04/23 Mrs Smith Ch22 The delivery of nutrients to cells
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Learning Intentions
To understand how the liver, lungs and kidneys are involved in the removal of materials from the blood.
Success Criteria5. Explain the mechanism
of kidney function to include
II. Re-absorption
8. ReabsorptionAbout 180 l of glomerular filtrate is produced every day but only 1-2 l of urine is produced, because ~ 99% of the water in the filtrate is reabsorbed into the bloodstream.
Reabsorption occurs at various points along the tubule that come into contact with the blood capillaries.
Apart from the plasma proteins and water, the chemicals in blood plasma and glomerular filtrate are very similar.
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A. Reabsorption of Salts: Reabsorption of Salts: Proximal convoluted tubule
Glucose & amino acids absorbed by epithelial cells lining the tubule.
90% Sodium ions (Na+) from glomerular filtrate actively pumped across epithelial cells, as they are combined with Chloride (Cl-) ions in the form of salt, they to pass into the blood
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Facilitateddiffusion
Activetransport
Diffusion
Sodium ions in thelumen of
the proximalconvoluted tubule
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A. Reabsorption of Water: Reabsorption of Water: Proximal convoluted tubuleProximal convoluted tubule
Water The active transport of glucose, sodium ions (and other solutes such as amino acids) into the blood stream reduces the blood plasma's concentration relative to that of the glomerular filtrate.
Water therefore passes into blood by osmosis.
This movement of water is a form of passive transport and does not require energy. About 85% of water is reabsorbed from the proximal convoluted tubule. 19/04/23 52
The transport of glucose, amino acids and ions into the epithelial cells creates a gradient of water
potential across the lining of the tubule; water is therefore withdrawn from the tubule by osmosis,
such that approximately 85%of the filtered fluid is reabsorbed back into the blood
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Epithelial cells are structurally suited to their function:
Image source: people.eku.edu
Many mitochondria to provide energy for active transport (of glucose)
Many microvilli for large surface area
Reabsorption of Glucose : Reabsorption of Glucose : Proximal convoluted tubuleProximal convoluted tubule
19/04/23 54
Carrier molecules carry glucose across cell membranes
lumen
epithelialcells
microvilli
intercellular
spaces
manymitochondri
a
interstitial fluid
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DiabetesDiabetesUntreated sufferers of diabetes mellitus have so much glucose in their blood plasma that some of the glucose in the glomerular filtrate is not reabsorbed by the epithelial cells of the proximal convoluted tubules. This is excreted in urine.
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B. Reabsorption: Loop of HenleB. Reabsorption: Loop of Henle• Each U-shaped loop of Henle lies in
the medulla• Consists of a descending limb and
an ascending limb• At the descending limb
– Water is reabsorbed back into the bloodstream by Osmosis
– Salts are not reabsorbed here
• At the ascending limb– water is not reabsorbed as the thick
wall of the tubule is impermeable to water
– Salts are pumped out of the filtrate into the tissue fluid
57
This creates a low water concentration by high solute concentration
C. Reabsorption: Distal convoluted tubuleC. Reabsorption: Distal convoluted tubule
Sodium chloride (salt) is reabsorbed from the distal convoluted tubule by being actively pumped into the bloodstream, but in smaller quantities.
Water also passes from the distal convoluted tubule into the bloodstream
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D. Reabsorption: Collecting DuctD. Reabsorption: Collecting DuctBecause the medullary tissue fluid has a low water concentration (due to the action at the ascending limb of the loop of Henle) the kidney tissues can reabsorb lots of water by osmosis from the collecting ducts. The volume of water needed to return the bloods water concentration to normal is reabsorbed from the filtrate. The rest is passed out in the urine. 19/04/23 59
ADH Present - Collecting Duct is permeable to water and a small
volume of urine is produced
No ADH Present - Collecting Duct is NOT permeable to water and
large volume of urine is produced
D. Reabsorption from Collecting Duct D. Reabsorption from Collecting Duct is controlled by the hormone ADHis controlled by the hormone ADH
Image source: www.uic.edu
19/04/2360Mrs Smith Ch23 The Removal of
Materials from Blood
Reabsorption – Summary• Proximal convoluted tubule
– Glucose Active Transport
– Salt (Sodium+Chloride ions) Active Transport– Water Osmosis
• Descending Loop of Henle– Water Osmosis
• Ascending Loop of Henle – Salts (Sodium+Chloride ions) Active Transport
• Distal Convoluted Tubule– Salts (Sodium+Chloride ions) Active Transport– Water Osmosis19/04/23 61
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Learning Intentions
To understand how the liver, lungs and kidneys are involved in the removal of materials from the blood.
Success Criteria6. Analyse data on
glomerular filtrate, tubule fluid and urine composition and rates of production
Water content of blood normal
High volume of water passes into blood
Low volume of water passes into blood
High volume of water reabsorbed by kidney
Low volume of water reabsorbed by kidney
Water content of blood too low
Water content of blood too high
Salt eaten or much sweating
Too much water drunk
Role of Role of ADHADH
Small volume of concentrated urine passed to the bladder
High volume of dilute urine passed to the bladder
Brain releases much ADH
Brain releases little ADH
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ADH and OsmoregulationADH and Osmoregulation
The volume of water reabsorbed varies greatly. This is regulated by the concentration of anti-diuretic hormone (ADH) present in the bloodstream.
ADH increases the
permeability to water of the
distal convoluted tubules & collecting
ducts.
Image source: www.bbc.co.uk
Regulation of Blood Water Concentration19/04/23 64Mrs Smith Ch23 The Removal of
Materials from Blood
• When the water concentration of the blood is high, very little ADH is released into the blood stream from the pituitary gland.
• The distal convoluted tubules and collecting ducts remain practically impermeable to water and almost none is reabsorbed from these regions of tubule.
• A large volume of dilute urine is therefore. produced
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ADH and OsmoregulationADH and OsmoregulationHigh Water ConcentrationHigh Water Concentration
• When the water concentration of the blood is low, the situation is reversed and a small volume of concentrated urine is produced.
• This mechanism allows the kidneys to plat an osmoregulatory role in the maintenance of the body’s internal steady state. (more in chapter 24)
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ADH and OsmoregulationADH and OsmoregulationLow Water ConcentrationLow Water Concentration
Task: Torrance-TYK pg183 Qu 1-3
19/04/23 67Mrs Smith Ch20: Transport Mechanisms - The Cardiac Cycle
Task: Torrance AYK pg184/185 Qu’s 1-6
19/04/23 68Mrs Smith Ch19 The need for transport
Essay Questions:SQA 2005
2005
Describe the function of the liver under the following headingsi.Production of urea. (2)
ii.Metabolism of carbohydrates. (5)
iii.Breakdown of red blood cells.(3)
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Guide to ‘H’ Grade EssaysEssay 35 pg83
Discuss the role of the liver under the following headingsi.Metabolism of protein.(5)
ii.Detoxification. (5)
iii.Conservation of useful substances (5)
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Guide to ‘H’ Grade EssaysEssay 35 pg83
Give an account of the role of the kidneys with reference to the following:i.Ultrafiltration. (8)
ii.Reabsorption. (7)
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TASK: Match the correct word with its meaning on each page!
Word MeaningKidney
Renal artery
Renal vein
Ureter
Bladder
Urethra
ADH
Hormone
Pituitary gland
Carries unpurified blood to the kidney
Carries purified blood away from the kidney
Chemical messengerCarries urine from the kidney to the
bladderGland that releases ADHStores urineCarries urine out of bodyOrgan that filters the bloodHormone that regulates water
balance
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Word Meaning
Glomerulus
Bowman’s capsule
Blood capillaries
Nephron
Loop of Henle
Network of very thin blood vessels
U-shaped kidney tubule that reabsorbs water into the bloodstream
Tiny knot of blood capillaries in the Bowman’s capsule where filtration of the blood occurs
Cup-shaped structure that collects glomerular filtrate from the blood
Tiny filtering unit in the kidney19/04/23 74Mrs Smith Ch23 The Removal of
Materials from Blood
Word Meaning
Collecting duct
Dialysis
Glomerular filtrate
Urine
Urea
Waste liquid excreted by the body
Tube that carries urine away from several kidney tubules
Nitrogen containing waste product made in the liver from surplus amino acids
Fluid produced from filtration of the blood in a glomerulus
Artificial filtration of blood through a selectively permeable membrane to remove waste products19/04/23 75Mrs Smith Ch23 The Removal of Materials from Blood