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3.12 The Excretory System

3.12 The Excretory System. Pages 210-214. Kidneys. The kidney is the size of a fist and a mass of approximately 500 grams. Metabolic Waste. Waste is produced from the break-down of proteins. Deamination. We eat protein. We use protein for building and repair.

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3.12 The Excretory System

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  1. 3.12 The Excretory System Pages 210-214

  2. Kidneys • The kidney is the size of a fist and a mass of approximately 500 grams.

  3. Metabolic Waste • Waste is produced from the break-down of proteins.

  4. Deamination • We eat protein. • We use protein for building and repair. • The liver breaks down extra protein. • The amino group, NH2 , is converted to ammonia, NH3 ,

  5. Toxic • The amino group, NH2 , is converted to ammonia, NH3 • Ammonia is toxic! 0.005 mg can kill you!

  6. Solution… • Combining ammonia with carbon dioxide makes urea, [NH2]2CO • Urea is less toxic than ammonia • The blood carries urea to the kidneys where it is excreted in the urine

  7. Kidneys • Filter blood

  8. Renal arteries • Bring blood to the kidney.

  9. Renal Veins • Return “cleaned” blood to the circulatory system.

  10. Ureters • Carry urine from the kidneys to the Bladder.

  11. Bladder control • A sphincter at the base controls the bladder • 200 mL …signal sent “Go to the bathroom” • 400 mL …urgent signal sent “ Go to the bathroom right now!” • 600 mL …too late

  12. Ureter • The tube that carries urine from the bladder to the exterior of the body.

  13. Urine formation • Step #1 filtration • Step #2 reabsorption • Step #3 secretion

  14. Nephrons • One million per kidney

  15. Bowman’s capsule • The cup-like structure that surrounds the glomerulus.

  16. The glomerulus • Cluster of capillaries • The area of fluid filtration

  17. Proximal tubule • a hollow, winding large diameter tube • for the reabsorption of glucose, sodium, amino acids • these are pumped back into the capillaries • urea stays in the tube

  18. Descending loop of Henle • Straight part of the loop moving away from the proximal tubule • Water flows out by osmosis

  19. Ascending Loop of Henle • Straight part of loop heading to distal tubule • Sodium pumped out of tube

  20. Distal tubule • A hollow winding large diameter tube. • Reabsorption of water if needed.

  21. Collecting Duct • System of urine collecting ducts that widen as they near the renal pelvis • Wastes are transferred from the capillary network to the duct. • Water moves by osmosis from the duct to the surrounding blood.

  22. #1 Filtration Moves from glomerulus to Bowman’s capsule: • Water • Salt • Glucose • urea

  23. #1 Filtration Does not move from glomerulus to Bowman’s capsule: • Plasma proteins • Blood cells • Large platelets

  24. volume • 600 mL blood through each kidney per minute

  25. Reabsorption • 119 of every 120 mL of fluid is returned to the blood

  26. Urine • 95% water • 5% salts, urea etc.

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