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Excretion

Excretion. Section 7.3 Page 342. Excretion. The elimination of wastes and unwanted materials from the body. The body needs to remove certain substances: metabolic wastes ingested toxins. Two important metabolic waste products. Ammonia Waste product of protein metabolism Highly toxic

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Excretion

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  1. Excretion Section 7.3 Page 342

  2. Excretion • The elimination of wastes and unwanted materials from the body. • The body needs to remove certain substances: • metabolic wastes • ingested toxins

  3. Two important metabolic waste products • Ammonia • Waste product of protein metabolism • Highly toxic • Urea • Ammonia is converted to urea to lower toxicity

  4. Ammonia • Excess protein is converted to carbohydrates • Carbohydrate general formula: [CH2O]x • Amino acid general structure: • Amino group needs to be removed first: deamination

  5. Waste product of deamination is ammonia (NH3) • Ammonia is highly toxic • Excreted in urine • But, since urine is stored in the bladder, the toxicity of ammonia must first be reduced. • It is converted to urea

  6. Urea • In the liver, ammonia gets converted to urea: 2 NH3+ CO2 (intermediates) (NH2)2CO • Urea is far less toxic than ammonia • Excreted in urine ammonia urea

  7. Other metabolic waste products:

  8. Ingested toxins Examples: • Alcohol • Drugs • Heavy metals • Toxins are primarily processed by liver • Goal: Make substances more polar, so they are soluble

  9. The Urinary System Section 7.4 Page 346

  10. The kidneys • The major organ of the urinary system • The kidneys have two functions: • Remove wastes from body • Maintain water balance

  11. Waste removal How is it accomplished? Multistep process: • Filtration of wastes from blood into tubules in kidneys • Formation of urine within kidneys • Storage of urine by bladder • Excretion

  12. Renal anatomy Renal arteries • Branch from aorta • Bring blood to kidneys • Renal artery

  13. Renal anatomy (2) Kidneys • Fist-shaped • 0.5 kg each • Two distinct layers: • the cortex (outer) • the medulla (inner) • Interior hollow chamber: the renalpelvis • Functional units are the nephrons • Renal artery

  14. Renal anatomy (2.5) Kidneys • Fist-shaped • 0.5 kg each • Two distinct layers: • the cortex (outer) • the medulla (inner) • Interior hollow chamber: the renalpelvis • Functional units are the nephrons

  15. Renal anatomy (3) Ureters • Bring filtered waste (urine) to the urinary bladder • Connect to the kidney within the renal pelvis • Renal artery

  16. The nephron • Nephrons are tubules • The functional unit of the kidneys • About 1 million per kidney • Responsible for formation of urine from filtered wastes

  17. The nephron: anatomy The blood vessels • Afferent arterioles • Efferent arterioles • Glomerulus • A high-pressure capillary bed • Peritubular capillaries • Network that wraps around the nephron tubule Peritubular capillaries

  18. The nephron: anatomy The tubules • The Bowman’s capsule • Proximal tubule • Loop of Henle, LoH • Distal tubule • Collecting ducts

  19. The nephron extends downwards into the kidney: • Glomerulus, proximal tubule, and distal tubule in the cortex. • Loop of Henle and collecting duct descend into the medulla.

  20. Homework • Pg. 348 #3, 4

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