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Excretion

Excretion. The process by which the body rids itself of metabolic wastes. Lungs eliminate carbon dioxide Large intestine eliminates toxic digestive waste. 3 . Liver deaminates amino acids to form ammonia (NH 3 ). -Ammonia is toxic so it is converted into urea.

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Excretion

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  1. Excretion

  2. The process by which the body rids itself of metabolic wastes • Lungs eliminate carbon dioxide • Large intestine eliminates toxic digestive waste

  3. 3. Liver deaminates amino acids to form ammonia (NH3)

  4. -Ammonia is toxic so it is converted into urea. -Nucleic acids break down into uric acid.

  5. 4. Kidneys-remove urea and uric acid

  6. The Urinary System • Two kidneys • Ureters – tubes from kidney to bladder • Bladder – stores urine • Urethra – from bladder to exterior

  7. The Kidneys • Function: to remove metabolic wastes from blood • Also regulate pH and water balance of blood

  8. The Nephron • Microscopic filters – 1 million in each kidney!

  9. Each kidney has 3 regions: • Cortex – outermost • Contains most parts of nephrons

  10. 2) The medulla: middle region • Contains loops of Henle, collecting ducts of nephrons

  11. 3)The renal pelvis: the mostly hollow innermost region • Collecting ducts merge to form ureter

  12. The Urinary System • Ureters have muscular walls – peristalsis • About 25 cm long

  13. The Urinary System • The urinary bladder – holds up to 600 mL

  14. Urinary System • Urethra is longer in males (20 cm vs. 4 cm)– thus less infections get to bladder

  15. The Urinary System • Micturition: the voluntary release of sphincters controlling the urine output from bladder • Also aided by contraction of bladder wall

  16. Formation of Urine • done by the nephrons • three stages: filtration, absorption and secretion.

  17. Filtration • High blood pressure in the glomerulus forces small molecules out of the blood and into Bowman’s Capsule • Water, ions like Na+, Cl- and H+, amino acids, urea and glucose can pass into Bowman’s capsule

  18. Filtration • Red blood cells, white blood cells and platelets can not move into Bowman’s capsule. • (If they do it is a sign that something is wrong.)

  19. Filtration • About 45 gallons (180 L ) per day passes through Bowman’s capsule. • But only 1-2 L of urine is formed so what happens next?

  20. Reabsorption • Essential nutrients and water are reabsorbed into the blood stream and distributed to the body. • main site: proximal convoluted tubule • also occurs in the loop of Henle, distal tubule and collecting ducts

  21. Reabsorption • Na+ is moved back into the blood by active transport- requires energy • Negative ions like Cl- will follow the Na+ due to charge attraction • Glucose and amino acids are also reabsorbed by active transport

  22. Active transport may form vesicles

  23. Reabsorption • The movement of solutes back into the blood creates an osmotic gradient so that water also moves into the blood by osmosis.

  24. Secretion Secretion – actively transporting materials back into urine from the blood. Ex) nitrogenous waste, water • Occurs in the proximal and distal tubules.

  25. Proximal tubule secretes H+ which helps maintain pH balance Blood is neutral and H+ makes it acidic so it must be removed. Secretion

  26. Secretion • Other things secreted include ammonia, potassium ions, penicillin, histamines, creatine, etc. Histamine release from a WBC Penicillin capsules

  27. Hormonal Control 1) Aldosteroneis secreted from the cortex of the adrenal glands when blood pressure is low.

  28. Hormonal Control • Low B.P is monitored by kidneys (juxtaglomerular complex)

  29. Hormonal Control • Aldosterone causes the DCT and collecting ducts to increase Na+ transport into blood • Chloride ions and water follow passively

  30. Hormonal Control • Net result: Blood pressure increases and urine output decreases

  31. Hormonal Control 2) Antidiuretic Hormone (ADH) • Produced by hypothalamus, stored in posterior pituitary gland

  32. Hormonal Control • Hypothalamus monitors water content of blood (osmoreceptors) • When the body is dehydrated, ADH is released.

  33. Hormonal Control • ADH makes the nephron more permeable to water so more water is reabsorbed into the blood. • As a result, the urine becomes more concentrated. • When the body is well hydrated, the hypothalamus does not release ADH

  34. Diuretics like alcohol and caffeine inhibit ADH production • So urine output increases

  35. Diabetes Mellitis • inadequate secretion of insulin • without insulin, blood glucose levels are extremely high, and excess glucose remains in the nephron.

  36. The high osmotic gradient prevents water re-absorption and increases urine production. • Sugar is found in the urine

  37. Diabetes Insipidus • lack of ADH production • urine output increases up to 20L/day • no sugar in urine

  38. Nephritis • inflammation of the nephrons • Protein in the urine is a common symptom • The osmotic gradient also causes an increase in urine production. • Nephritis can lead to irreversible kidney damage and eventual kidney failure.

  39. Dialysis Hemodialysis • Artificial kidney machine connects to a vein and pumps blood through semipermeable tubes submerged in a solution to remove waste

  40. Dialysis • Peritoneal dialysis-a catheter is inserted through abdominal lining. • Fluid is injected to collect waste and is drained

  41. Kidney Stones • Crystallized oxalic acid and/or calcium and/or phosphate • Painful!

  42. Kidney Stones Treatment: • Surgical removal • Drugs to dissolve • Lithotripsy-shock waves

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