1. Learning Goal: I will describe the anatomy and physiology of the excretory system and how it maintains homeostasis w.r.t water, ionic and pH balance. Kidney Structure & Function The kidneys have three basic mechanisms for separating the various components of the blood: –filtration, reabsorption, and secretion. The structure of the kidney is such that it allows for this function Interactive video

2. Watch the interactive video and label what happens to urea, glucose, water, protein and sodium as they enter the nephron, also, text pp. 346 - 356

3. Function of the parts of the Nephron Glomerulus – a network of capillaries with a semi-permeable membrane, the main filter, blood is transported in through (select one, Q1) –A) afferent arteriole. –B) efferent arteriole. –C) renal artery. –D) renal vein Water and dissolved solutes go into Bowman’s capsule of nephron tubule to make up filtrate (blood cells and proteins do not)

4. Question 2: What occurs in the ascending limb of the loop of Henle? a)Urea is reabsorbed b)Water is reabsorbed c)Water is secreted d)It is impermeable to water e)It is impermeable to sodium f)Water follows a concentration gradient

5. Water balance Key hormone: Antidiuretic hormone (ADH), also called Vasopressin, comes from the pituitary gland in the brain –Question 3: “Antidiuretic” means a)Against water in the blood b)Against water in the urine c)Against dying d)Against waste in the urine

6. Plasma ADH levels low -> large volume of urine excreted (diuresis) and it’s dilute Plasma ADH levels high ->small volume of urine excreted (antidiuresis) and it’s concentrated

7. Yes or No Question 4 You drank a lot of water. ADH levels in the body would be high.

8. 5. Multiple Answer Question: Your body senses that your blood has a high OSMOLALITY select the most probable effectors: a)You will feel thirsty b)You will feel tired c)ADH will be inhibited d)ADH is released e)There will be a higher concentration of aquaporin channels in the nephron f)There will be a lower concentration of aquaporin channels in the nephron

9. Osmoreceptors in hypothalamus sense osmolality ([ion]) of blood plasma Message is sent to pituitary gland to release ADH into bloodstream ADH stimulates transcription and opening of aquaporin channels in collecting duct cells (to allow water to be reabsorbed)

10. 6. Yes or No Question: ADH is released when osmolality is high.

11. ADH travels to C.D. cells It stimulates a receptor which sends a signal to the nucleus This signal stimulates more aquaporin transcription and translation

12. Another hormone involved in H 2 O/solute balance p. 354 The kidneys play a role in BP by adjusting Blood Volume Aldosterone - from adrenal glands (above kidneys) –acts on distal tubule and collecting duct, promotes sodium reabsorption, –this  ion and water retention which  blood V and P.

13. Question 7: True or False When a person sweats and does not drink water, the pituitary gland releases aldosterone. Question 8: True or False The hormone aldosterone increases water reabsorption.

14. Renal Regulation of pH We consume foods of varying pH Cells produce CO 2 which forms carbonic acid in the blood There is a buffer system in the blood that counteracts (buffers) changes in pH H + + HCO 3 -  H 2 CO 3  H 2 O + CO 2

16. Proximal Tubule It is involved in acid-base balance in 2 ways: 1. Reabsorbs bicarbonate which is filtered at the glomerulus 2. Produces ammonium (this removes H + from circulation)

17. Question 9: Excess hydrogen ions H+ are removed by a. proximal tubule after reaction with ammonia b. distal tubules after reaction with urea c. water d. the lungs after reaction with bicarbonate ions e. the presence of ADH

18. Question 10: T/F All animals produce nitrogenous waste due to protein breakdown Question 11: T/F Urine is formed within the glomerulus, which is the functional unit of the kidney. Question 12: T/F Filtrate flows from the proximal convoluted tubule to the collecting duct, the next site where additional water is reabsorbed

19. Question 13: T/F The renal vein supplies the kidney with blood. Question 14: T/F The enzyme, carbonic anhydrase, would be found in the filtrate.

20. Question 15: Which of the following are components of the first part of the nephron? A) Capillary network called glomerulus B) afferent arteriole C) Renal artery D) efferent arteriole E) Bowman’s capsule F) ureter

21. Question 16: An increase in BP in the glomerulus would cause A) an increase in filtration and increase in urine output B) an increase in filtration and decrease in urine output C) a decrease in filtration and decrease in urine output D) no effect on urine output

22. Question 17: Nitrogen wastes from the breakdown of proteins and amino acids are removed from the body by the A) conversion of ammonia to urea in the liver and filtration by the kidney B) conversion of ammonia to urea in the kidney and filtration by the kidney C) conversion of ammonia to urea in the liver and secretion by the kidney D) conversion of urea to ammonia in the kidney and secretion by the kidney

23. Question 18: T/F The renal medulla has high osmolality Question 19: Which of the following parts of the nephron are found in the medulla of the kidney? (select all that apply) A) glomerulus B) proximal tubule C) descending loop of Henle D) ascending loop of Henle E) distal convoluted tubule F) collecting duct

24. Read: Structure and Function of the Nephron pp. 346 – 356 Do: Pg. 356 #1, 2, 4, 8, 10