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The Mammalian Excretory System

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

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The Mammalian Excretory System

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  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/images/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 • Each kidney contains about one million nephrons • Spans cortex and medulla • Sac with long tube leading to ureter http://www.bbc.co.uk/scotland/education/bitesize/standard/img/biology/kidney_function1.gif

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

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

  11. Nephron consists of five parts: • Bowman’s capsule • Proximal tubule http://www.bbc.co.uk/scotland/education/bitesize/standard/img/biology/kidney_function1.gif

  12. Nephron consists of five parts: • Bowman’s capsule • Proximal tubule • Loop of Henle http://www.bbc.co.uk/scotland/education/bitesize/standard/img/biology/kidney_function1.gif

  13. Nephron consists of five parts: • Bowman’s capsule • Proximal tubule • Loop of Henle • Descending branch http://www.bbc.co.uk/scotland/education/bitesize/standard/img/biology/kidney_function1.gif

  14. Nephron consists of five parts: • Bowman’s capsule • Proximal tubule • Loop of Henle • Descending branch • Ascending branch http://www.bbc.co.uk/scotland/education/bitesize/standard/img/biology/kidney_function1.gif

  15. Nephron consists of five parts: • Bowman’s capsule • Proximal tubule • Loop of Henle • Descending branch • Ascending branch • Distal tubule http://www.bbc.co.uk/scotland/education/bitesize/standard/img/biology/kidney_function1.gif

  16. Also have collecting duct: • Collects urine from distal tubule • Passes through medulla • Discharges to renal pelvis http://www.bbc.co.uk/scotland/education/bitesize/standard/img/biology/kidney_function1.gif

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

  18. And blood vessels • Afferent arteriole http://www.bbc.co.uk/scotland/education/bitesize/standard/img/biology/kidney_function1.gif

  19. And blood vessels • Afferent arteriole • Glomerulus http://www.bbc.co.uk/scotland/education/bitesize/standard/img/biology/kidney_function1.gif

  20. And blood vessels • Afferent arteriole • Glomerulus • Efferent arteriole http://www.bbc.co.uk/scotland/education/bitesize/standard/img/biology/kidney_function1.gif

  21. And blood vessels • Afferent arteriole • Glomerulus • Efferent arteriole • Peritubular capillaries http://www.bbc.co.uk/scotland/education/bitesize/standard/img/biology/kidney_function1.gif

  22. Major processes of nephron • Filtration • Secretion • Reabsorption • Excretion http://www.bbc.co.uk/scotland/education/bitesize/standard/img/biology/kidney_function1.gif

  23. At the glomerulus • Blood is filtered • 2000 L/day • Raw urine passes into capsule space • 180 L/day • Remaining blood flows into efferent arteriole http://coe.fgcu.edu/faculty/greenep/kidney/glomer3.jpg

  24. At the proximal tubule • Useful molecules (sugars, amino acids, bicarbonate, potassium) are resorbed from filtrate into blood • Na+ is resorbed by active transport • Cl- and water follow passively • Urine is iso-osmotic to blood http://renux.dmed.ed.ac.uk/EdREN/makingimages/NephronS.gif

  25. Making hyperosmotic urine Concentrated

  26. Making hyperosmotic urineStep 1 • In ascending branch, Na+ is resorbed by active transport • Cl- follows passively • Water stays behind • Urine becomes more dilute • Medulla tissue becomes more salty - giving gradient Cl- Na+ http://renux.dmed.ed.ac.uk/EdREN/makingimages/NephronS.gif

  27. Making hyperosmotic urineStep 2 • In descending branch, urine enters salty medulla • Water diffuses from tubule • Urine becomes more concentrated H2O H2O http://renux.dmed.ed.ac.uk/EdREN/makingimages/NephronS.gif

  28. Making hyperosmotic urineStep 2 • In descending branch, urine enters salty medulla • Water diffuses from tubule • Urine becomes more concentrated H2O H2O Opposite flow in loop of Henle magnifies saltiness in tissue, giving “Countercurrent Multiplier” effect.

  29. Making hyperosmotic urineStep 3 H+ K+ • In distal tubule, urine is hypo-osmotic to blood • H+ and K+ are secreted into tubule • Urine becomes more acidic http://renux.dmed.ed.ac.uk/EdREN/makingimages/NephronS.gif

  30. Making hyperosmotic urineStep 4 • In collecting duct, watery urine passes through salty medulla. • H2O leaves, assuming antidiuretic hormone (ADH) is present • Urine becomes more concentrated H2O H2O http://renux.dmed.ed.ac.uk/EdREN/makingimages/NephronS.gif

  31. Making hyperosmotic urineStep 4 • In collecting duct, watery urine passes through salty medulla. • H2O leaves, assuming antidiuretic hormone (ADH) is present • Urine becomes more concentrated H2O H2O Note: ADH allows us to retain water under normal circumstances

  32. ADH may not be present • Excessively dilute urine or alcohol in blood cuts off flow of ADH from posterior pituitary • Collecting ducts do not resorb water • Watery urine leaves collecting duct http://renux.dmed.ed.ac.uk/EdREN/makingimages/NephronS.gif

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

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