1. The Mammalian Excretory System Principles of Modern Biology II At Wilkes University Kenneth M. Klemow, Ph.D.

2. One problem: Mammalian blood contains metabolic waste products that must be removed - without removing useful materials. http://mdc.mo.gov/kids/out-in/1998/1/back3.jpg

3. Another problem: Terrestrial mammals must maintain a relatively constant osmotic level. Living on land promotes desiccation; thus must retain water. Occasionally we have excess water and must excrete it. http://www.fairfaxcounty.gov/dpwes/image s/recycling/giraffecolor.jpg

4. The solution Mammals have an excretory system that removes waste products and maintains osmotic balance.

5. Mammalian excretory system Kidneys Ureters Urinary bladder Urethra http://upload.wikimedia.org/wikipedia/commons/thumb/1/ 18/Illu_urinary_system.jpg/300px-Illu_urinary_system.jpg

6. The mammalian kidney Cortex Medulla Renal pelvis Renal pyramids Blood vessels Renal artery Renal vein Ureter http://research.surgery.wisc.edu /southard/organs/kidney.gif

7. The mammalian kidney Have gradient of increasing salinity from cortex to medulla http://research.surgery.wisc.edu /southard/organs/kidney.gif

8. Nephron: basic urine- producing unit of kidney zEach kidney contains about one million nephrons zSpans cortex and medulla zSac with long tube leading to ureter http://www.bbc.co.uk/scotland/education/bitesize/stand ard/img/biology/kidney_function1.gif

9. Nephron consists of five parts: http://www.bbc.co.uk/scotland/education/bitesize/stand ard/img/biology/kidney_function1.gif

10. Nephron consists of five parts: zBowman’s capsule http://www.bbc.co.uk/scotland/education/bitesize/stand ard/img/biology/kidney_function1.gif

11. Nephron consists of five parts: zBowman’s capsule zProximal tubule http://www.bbc.co.uk/scotland/education/bitesize/stand ard/img/biology/kidney_function1.gif

12. Nephron consists of five parts: zBowman’s capsule zProximal tubule zLoop of Henle http://www.bbc.co.uk/scotland/education/bitesize/stand ard/img/biology/kidney_function1.gif

13. Nephron consists of five parts: zBowman’s capsule zProximal tubule zLoop of Henle yDescending branch http://www.bbc.co.uk/scotland/education/bitesize/stand ard/img/biology/kidney_function1.gif

14. Nephron consists of five parts: zBowman’s capsule zProximal tubule zLoop of Henle yDescending branch yAscending branch http://www.bbc.co.uk/scotland/education/bitesize/stand ard/img/biology/kidney_function1.gif

15. Nephron consists of five parts: zBowman’s capsule zProximal tubule zLoop of Henle yDescending branch yAscending branch zDistal tubule http://www.bbc.co.uk/scotland/education/bitesize/stand ard/img/biology/kidney_function1.gif

16. Also have collecting duct: zCollects urine from distal tubule zPasses through medulla zDischarges to renal pelvis http://www.bbc.co.uk/scotland/education/bitesize/stand ard/img/biology/kidney_function1.gif

17. And blood vessels http://www.bbc.co.uk/scotland/education/bitesize/stand ard/img/biology/kidney_function1.gif

18. And blood vessels zAfferent arteriole http://www.bbc.co.uk/scotland/education/bitesize/stand ard/img/biology/kidney_function1.gif

19. And blood vessels zAfferent arteriole zGlomerulus http://www.bbc.co.uk/scotland/education/bitesize/stand ard/img/biology/kidney_function1.gif

20. And blood vessels zAfferent arteriole zGlomerulus zEfferent arteriole http://www.bbc.co.uk/scotland/education/bitesize/stand ard/img/biology/kidney_function1.gif

21. And blood vessels zAfferent arteriole zGlomerulus zEfferent arteriole zPeritubular capillaries http://www.bbc.co.uk/scotland/education/bitesize/stand ard/img/biology/kidney_function1.gif

22. Major processes of nephron zFiltration zSecretion zReabsorption zExcretion http://www.bbc.co.uk/scotland/education/bitesize/stand ard/img/biology/kidney_function1.gif

23. At the glomerulus zBlood is filtered y2000 L/day zRaw urine passes into capsule space y180 L/day zRemaining blood flows into efferent arteriole http://coe.fgcu.edu/faculty/greenep/kidney/glomer3.jpg

24. At the proximal tubule zUseful molecules (sugars, amino acids, bicarbonate, potassium) are resorbed from filtrate into blood zNa + is resorbed by active transport zCl - and water follow passively zUrine is iso-osmotic to blood http://renux.dmed.ed.ac.uk/EdREN/makingi mages/NephronS.gif

25. Making hyperosmotic urine Concentrated

26. Making hyperosmotic urine Step 1 zIn ascending branch, Na + is resorbed by active transport zCl - follows passively zWater stays behind zUrine becomes more dilute zMedulla tissue becomes more salty - giving gradient Na + Cl - http://renux.dmed.ed.ac.uk/EdREN/makingi mages/NephronS.gif

27. Making hyperosmotic urine Step 2 zIn descending branch, urine enters salty medulla zWater diffuses from tubule zUrine becomes more concentrated H2OH2O H2OH2O http://renux.dmed.ed.ac.uk/EdREN/makingi mages/NephronS.gif

28. Making hyperosmotic urine Step 2 zIn descending branch, urine enters salty medulla zWater diffuses from tubule zUrine becomes more concentrated H2OH2O H2OH2O Opposite flow in loop of Henle magnifies saltiness in tissue, giving “Countercurrent Multiplier” effect.

29. Making hyperosmotic urine Step 3 zIn distal tubule, urine is hypo-osmotic to blood zH+ and K+ are secreted into tubule zUrine becomes more acidic H+H+ K+K+ http://renux.dmed.ed.ac.uk/EdREN/makingi mages/NephronS.gif

30. Making hyperosmotic urine Step 4 zIn collecting duct, watery urine passes through salty medulla. zH2O leaves, assuming antidiuretic hormone (ADH) is present zUrine becomes more concentrated H2OH2O H2OH2O http://renux.dmed.ed.ac.uk/EdREN/makingi mages/NephronS.gif

31. Making hyperosmotic urine Step 4 zIn collecting duct, watery urine passes through salty medulla. zH2O leaves, assuming antidiuretic hormone (ADH) is present zUrine becomes more concentrated H2OH2O H2OH2O Note: ADH allows us to retain water under normal circumstances

32. ADH may not be present zExcessively dilute urine or alcohol in blood cuts off flow of ADH from posterior pituitary zCollecting ducts do not resorb water zWatery urine leaves collecting duct http://renux.dmed.ed.ac.uk/EdREN/makingi mages/NephronS.gif

33. Finally zSodium concentrations and blood pressure are regulated by hormones aldosterone and atrial natriuretic hormones zSee P. 1035-1036 of your text! http://www.nlm.nih.gov/medlinep lus/images/saltshaker.jpg