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Excretion

Excretion. What is Excretion?. The removal of metabolic waste products and excess substances from the body. CO 2 is a MWP of Respiration CO 2 is toxic in large amounts Excretion is NOT the same as Egestion The material in feces is not MWP’s; it was never digested or absorbed.

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Excretion

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  1. Excretion

  2. What is Excretion? • The removal of metabolic waste products and excess substances from the body. • CO2 is a MWP of Respiration • CO2 is toxic in large amounts • Excretion is NOT the same as Egestion • The material in feces is not MWP’s; it was never digested or absorbed.

  3. 3 Main Excretory Products • Do you remember them all? • Carbon Dioxide • MWP of cell Respiration • Urea • MWP of Liver, removed by kidneys • Water • In excess, removed by kidneys

  4. How do you Produce Urea? • First, you eat proteins, which get digested into amino acids and absorbed into your blood. • The AA’s travel to the Liver (thru the hepatic portal vein) • Extra AA’s get broken down into urea. • This involves deamination; removing the part of the AA that contains Nitrogen. • The part with N will be excreted as Urea. • So Urea is a “nitrogenous excretory product.”

  5. Urea Production & Excretion

  6. How do you Excrete Urea? • The urea goes back into the blood and travels to the kidneys. • Kidneys take urea out of the blood and mix it with water to make urine. • The urine flows from the kidneys thru 2 ureters to the bladder. • Then it’s excreted thru the urethra.

  7. Urea Production & Excretion

  8. Human Urinary System

  9. Real Quick Review • You eat a protein and break it down into AA’s. Where do the AA’s go next? • To the Liver (thru the HPV) • What happens to extra AA’s in the Liver? • They get deaminated and made into urea • Where does the urea go next? • To the kidneys, then out of the body thru the ureters  bladder  urethra.

  10. Put them in order!  (pg. 140)

  11. More on Kidneys • Kidneys consist of tiny units of tubules called nephrons. • The nephron is where urea is filtered out of the blood. • An intricate network of blood capillaries around the nephron helps urea diffuse down its concentration gradient into the urinary tubules. • Other substances also diffuse out of the blood in the same way.

  12. Kidney and Nephron

  13. Nephron and Blood Capillaries

  14. Kidney Failure • When kidneys fail, people still need their blood “cleaned” of urea and other harmful substances. • They have to undergo dialysis treatment several times a week. • Dialysis = a mechanical means of filtering blood, using concentration gradients to remove urea and other substances. • Blood is filtered outside of the body and pumped back in!

  15. Dialysis

  16. Dialysis

  17. Dialysis

  18. Kidneys and Water Regulation • What if you had too much water in your body? • What if you didn’t have enough? • Kidneys excrete lots of watery urine when you have too much. • Kidneys excrete only small amounts when you’re short on water. • So the urine is very concentrated.

  19. Other Excretory Substances (besides the 3 main ones) • Hormones • Broken down in liver, excreted by kidneys in urine • Alcohol • Also broken down in liver • Toxic to cells; even liver cells! • Liver damage or failure can result from drinking too much alcohol.

  20. Question (then we’re done!) • Why should a person with kidney failure avoid eating salty foods? • The kidneys will be unable to filter out the extra salt.

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