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Adam, Amy, Karl, Karlene, and Yifan
Excretory System
Introduction
http://www.youtube.com/watch?v=guOqyi5lUQQ (1:46-4:36)
Regulates bodily fluids, excreting and recycling waste Main organs: kidneys, ureters, bladder and urethra Disorders of the excretory system
Excretion
After metabolic activities (energy release, maintenance, repair) results in waste
Separating the needed and the unneeded or no longer needed
Skin, respiratory system, digestive system, excretory system
Major functions
of excretory system
Excretion of waste
Maintenance of
water and salt
pH control
Secretion of
hormones
Overall Major Functions
Functions: Excretion of Metabolic Waste
The average person urinates 3000 a year
Bladder can hold 16-24 ounces of urine
Nitrogenous waste Urea makes up the majority of
this waste
Functions: Maintenance of Water-Salt Balance
Maintain balance with water and salt in blood Regulating blood pressure Balance between potassium, bicarbonate and
calcium Cells need to stay in an isotonic solution
Functions: Maintenance of Acid-Base Balance
Buffer for blood Blood pH: 7.4 Urine is usually a pH of 6 Maintenance of alkaline reserve
Functions: Secretion of Hormones
Aids endocrine system in hormonal secretion
Calcitriol: Promotes calcium absorption
Erythropoiten: Production of red blood cells
Renin
Major Organs
Kidney (Nephron
s)
Ureter
Urinary
bladder Urethr
a
Organs
Kidneys: Lower back, filters waste from blood, functions named above
Ureter: Muscular tubes that carry urine Urinary Bladder: Urine is stored Urethra: Tube that urine is secreted from
Kidney: Introduction
Kidney: Pathway
Nephron
Kidney: Pathway
Filter Tubule Duct
Kidney: Filter
Renal artery enters Bowman’s capsule; glomerulus Walls of glomerulus are impermeable to large
molecules pressurized blood aids filtration
Small molecules are permeable The result is known as filtrate
Kidney: Tubule
Bowman’s capsule is connected to a looped tubule Divided into three parts
Proximal convoluted tubule Loop of Henle Distal convoluted tubule
Used by each nephron for reabsorption
Kidney: Tubule
Proximal convoluted tubule Uses ATP for active transport Drives sodium ions, glucose, and other solutes back
into the blood Water follows these substances into the blood by
osmosis
Kidney: Tubule
Loop of Henle
Kidney: Tubule
Loop of Henle Descending limb extends from within the renal
cortex into the renal medulla; extremely salty Permeable to water; water flows back into blood
Ascending limb is impermeable to water and slightly permeable to solutes Na+ diffuses out of the tubule and into nearby blood
vessels
Kidney: Tubule
In the thick-walled section, more Na+ is removed by active transport (uses ATP) Replenishes medulla’s salt Makes the filtrate less concentrated than surrounding
cortex tissue
Kidney: Tubule
1. Medulla is salty
2. Reabsorption of water causes salt concentration to decrease
3. ATP is used to actively reabsorb sodium ions
4. Increases osmolarity for future filtrate
Kidney: Tubule
Loop of Henle
Kidney: Tubule
Distal convoluted tubule Active reabsorption depends on the needs of the
body (sodium ions) Passive reabsorption of negative ions occurs by
electrical attraction (chloride) Potassium ions and hydrogen ions are actively
secreted by the body
Kidney: Duct
Tubule empties into a large pipe-like channel called a collecting duct Lowers back into the medulla; reabsorbs water
The size of the pores depends on signals from the brain
The result can now be called urine Reabsorbed substances are returned to the body
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The roles of ADH and aldosterone in regulating water
balance
Water Balance: Pituitary Gland
The pituitary gland is a gland at the base of the brain that sends signals to other glands and organs such as the thyroid gland, adrenal glands, ovaries, and testes Directs them to produce certain hormones Produces LD, ADH, FSH, and growth hormones
Water Balance: The Brain
Water Balance: Aldosterone
Aldosterone is a hormone that is produced by the adrenal glands
It works primarily on kidney (renal) cells to help maintain the balance of fluids and electrolytes in our bodies
It mainly works to control reabsorption of sodium and chloride and secretion of potassium and hydrogen
Water Balance: Aldosterone
Pathway: The role of aldosterone in sodium and water balance
is to regulate fluid and electrolyte balance When sodium and plasma volume is decreased, it
triggers the synthesis and secretion of aldosterone When sodium and plasma volume return to normal
levels, aldosterone secretion is reduced
Water Balance: Adrenal Gland
Water Balance: ADH
A hormone produced in the hypothalamus and secreted by the posterior pituitary gland
ADH stimulates reabsorption of water through the distal tubules and collecting ducts of the kidney, resulting in less water being excreted in the urine, thus conserving water
Water Balance: ADH
Pathway: Part of the brain, the hypothalamus, detects that
there is not enough water in the blood. The hypothalamus sends a message to the pituitary gland, which releases ADH. ADH travels from brain to the kidney and causes the kidneys to absorb more water and concentrate the urine. A lack of ADH results in increased urine volume and increased urination, a condition called diabetes insipidis.
Water Balance: ADH
ADH: antidiuretic hormone Pathway:
Part of the brain, the hypothalamus, detects that there is not enough water in the blood
The hypothalamus sends a message to the pituitary gland, which releases ADH
ADH travels from brain to the kidney and causes the kidneys to absorb more water and concentrate the urine
A lack of ADH results in increased urine volume and increased urination, a condition called diabetes insipidis.
Water Balance: Deficit
Water Balance: Surplus
Water Balance: End of Cycle
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Regulation of Blood pH
Maintaining Blood pH in the Excretory System
Blood pH: Introduction
The normal pH of blood is around 7.4 Allows our enzymes to function optimally
Failing to maintain homeostasis causes our blood pH to either increase or decrease This increase/decrease can result in serious medical
condition
Blood pH: Introduction
One way our blood pH can change in based on the foods/liquids we consume Blood pH can also changed from metabolic
processes Three main homeostatic mechanisms used to
maintain blood pH Acid-Base Buffer System Respiratory Centre Kidney Function
Blood pH: Acid-Base Buffer
Buffers blood; prevents changes in pH Takes up extra H+ ions of extra OH- ions that enter
the blood One of the most important buffer system involves
the use of carbonic acid and bicarbonate ions
Blood pH: Acid-Base Buffer
The system reacts differently depending on the presence of extra hydrogen ions of extra hydroxide ions
If H+ is added, the reaction that occurs is: H+ + HCO3
- H2C03
When OH- ions are added to blood: OH- + H2CO3 HCO3
- + H2O
Blood pH: Acid-Base Buffer
In the first reaction, the bicarbonate ion takes up excess hydrogen ion, in order to form carbonic acid
In the second reaction, water is produced Water will help maintain the blood pH, since water is
neutral These reactions temporarily prevent major
changes in pH
Blood pH: Respiratory Centre
The hydrogen ion concentration is raised, the respiratory centre (in the medulla oblongata) increases breathing rate It does this through specific signals that ensure our
breathing muscles contract and relax regularly Doing this causes the body to get rid of hydrogen
ions
H+ + HCO3- H2CO3 H2O + CO2
Blood pH: Respiratory Centre
When the reaction moves from carbon dioxide to hydrogen, the blood pH decreases and increases the other way
Increasing breathing causes carbon dioxide to be generated more quickly, decreasing the number of hydrogen ions
It is vital to have the correct proportion of carbonic acid to bicarbonate ions in blood
Breathing causes a readjustment so the proportion is correct so H+ and OH- can continue to be absorbed
Blood pH: Kidneys
The first two mechanisms are aided by powerful actions of the kidneys Only the kidneys are able to rid the body of a vast
range of acidic and basic substances Kidneys are slower acting, but have a more
powerful effect It is possible to urinate the excess acidic H+ ions or
basic HCO3- ions in order to raise or lower blood pH
Blood pH: Kidneys
Imagine the kidneys as releasing H+ and reabsorbing HCO3
- in order to maintain homeostasis
If blood is too acidic, H+ is released and HCO3- is
absorbed However, if blood is basic, neither is used
Another way of buffering is by using ammonia Removes hydrogen ions and adds in bicarbonate
ions NH3 + H+ NH4
+
Blood pH: Kidneys
Ammonia is produced in the tubule cells through the breakdown of amino acids
Ammonia works to produce ammonium ions For every ammonium ion that is produced, a new
HCO3− is made
Blood pH: Summary
There are three mechanisms used to maintain homeostasis, in terms of blood pH Acid-Base Buffer System Respiratory Centre Kidney Function
Each one has a unique way of doing so All three have advantages and disadvantages that
go along with them
Dialysis: Introduction
What is dialysis? Procedure that removes
wastes and excess fluid from the blood when kidney function is lost due to renal failure
Why is dialysis needed? Hyperkalemia
High potassium Hyperphosphatemia
High phosphate Uremia Edema
Dialysis: Two Types
Conclusion
The human excretory system is responsible for removing liquid waste from the body
The excretory system also regulates the acid-base balance and water-salt balance of the blood and secretes some hormones like ADH
The kidneys are composed of millions of functional units called nephrons that filter the waste from the blood and produce urine.
Dialysis is the procedure that removes wastes and excess fluid from the blood when kidney function is loss due to renal failure
Question #1
What is urine?
Answer
Filtrate of the nephron upon leaving the collecting duct; exits the body through the urethra
Question #2
What is a function in the excretory system that is involved in regulating blood pressure and the
appropriate potassium, bicarbonate, and calcium levels in blood?
Answer
Maintenance of Water-Salt Balance
Question #3
What is the role of ADH?
Answer
Stimulates reabsorption of water through the distal tubules and collecting ducts of the kidney Results in less water being excreted in urine
Question #4
What is the pituitary gland?
Answer
Gland at the base of the brain Send signals to other glands and organs to
produce certain hormones
Question #5
What is this picture showing?
Answer
Respiratory Centre Equation
Question #6
What is this picture showing?
Answer
The process of how the kidneys maintain the pH of blood
Question #7
Name the 2 types of dialysis. What are their differences?
Answer
Hemodialysis Removing wastes and excess fluids from the blood
by an external devices connected to an artery and a vein in a person’s arm.
For acute renal failure Peritoneal Dialysis
Removing wastes and excess fluids from the blood by inserting a catheter into the abdominal cavity.
For Chronic renal Failure
Question #8
What type of dialysis is this picture showing?
Answer
Hemodialysis
References
http://www.nhlbi.nih.gov/health//dci/Diseases/hlw/hlw_controls.html
http://h2g2.com/approved_entry/A8819652 https://www.inkling.com/read/textbook-of-medical-
physiology-guyton-hall-12th/chapter-30/combination-of-excess-h-with
Grade 12 Biology Textbook
Carter-Edwards, T., Gerards, S., Gibbons, K., McCallum, S., Noble, R., Parrington, J.,...Whyte-Smith, A. (2011). Biology 12. Canada, McGraw-Hill Ryerson, pp.444-462.
DeBruyne, L. K., Pinna, K., & Whitney, E. (2012). Nutrition & Diet Therapy (8thed.). United States, Wadsworth, Cengage Learning, pp595-607.
http://www.youtube.com/watch?v=cc8sUv2SuaY http://www.youtube.com/watch?v=WtrYotjYvtU http://www.webmd.com/a-to-z-guides/function-
kidneys http://science.howstuffworks.com/life/human-biolo
gy/kidney1.htm