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The Excretory System

The Excretory System. Biology 12 Ms. Marcos. Why excrete?. We need to get rid of waste products : CO2 Bile pigments and heme (from blood) Nitrogenous wastes from breakdown of amino acids Ammonia (NH 3 ) is VERY TOXIC NH 3 converted to urea in the liver (less toxic)

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The Excretory System

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  1. The Excretory System Biology 12 Ms. Marcos

  2. Why excrete? • We need to get rid of waste products: • CO2 • Bile pigments and heme (from blood) • Nitrogenous wastes from breakdown of amino acids • Ammonia (NH3) is VERY TOXIC • NH3 converted to urea in the liver (less toxic) • Urea is water soluble  excrete in urine

  3. Nitrogenous waste excretion

  4. Homeostasis… keeping things in balance What do we need to keep constant? • Temperature • Balance of major ions (salts) • Balance of water (Osmoregulation) • pH balance • Hormone secretion

  5. Structures involved in excretion • Lungs • Skin • Liver • Intestine • Kidneys!

  6. The Urinary System

  7. The Kidney

  8. THE KIDNEY Major parts of the kidney Renal medulla Renal cortex Renal pelvis Ureter

  9. Most systems produce urine by refining a filtrate derived from body fluids

  10. Basic steps to any excretory system • Filtration Use pressure to put things in the blood into a tube (make a filtrate) • Reabsorption take back the good stuff into the blood again • Secretion  add any extra toxins or other wastes that didn’t make it in the first time • Excretion  the filtrate leaves the system and goes out of the body

  11. The Nephron

  12. Renal cortex • ORIENTATION OF A NEPHRON WITHIN THE KIDNEY Major parts of the nephron Proximal tubule Bowman’s capsule Distal tubule Collecting duct Loop of Henle Renal medulla

  13. Filtration • Blood from an arteriole enters capillaries  the Glomerulus • High pressure forces parts of the blood into the Bowman’s capsule (the start of the nephron) • Small molecules get through (water, wastes, nutrients, ions) • Large molecules can not get through (proteins, blood cells)

  14. Reabsorption • Filtrate enters the proximal convoluted tubule • Take back the stuff you need: • Glucose • Sodium (Na+), Chlorine (Cl-) • Water • Amino acids • Leave the stuff you don’t want: • Some water • Nitrogenous wastes • Some salts (extra)

  15. 2 DETAILED STRUCTURE OF A NEPHRON Road map… check in

  16. On to the Loop of Henle… • 99% of water in the original filtrate is reabsorbed • The higher concentration of salts in the middle of the kidney helps bring water out

  17. Secretion • Filtrate enters the distal convoluted tubule • Any extra things you do not want enter the filtrate: • Chemicals or other toxins (drugs) • Excess ions • Not much flow of water

  18. Excretion • Filtrate enters the collection duct (it’s now urine) • Collecting duct is permeable to water, but not to salt • More water is brought back into the blood as the duct passes through the medulla • Enters ureter, then bladder, then through the urethra and OUT!

  19. Review… where did the urine come from?

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