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The Excretory System:
From Your Heart to the
Toilet
- Homeostasis: Regulation of a stable internal enviroment no
matter where we are or what we are doing.
- Kidneys
- Maintain levels of water and dissolved materials
- Control blood pressure
- Filter 180 litres of fluid but only 1.5 litres is peed out
- Renal Arteries: Blood enters kidneys from heart
- Maintain levels of water and dissolved materials
- Urethra
- Empties urine outside
- Empties urine outside
- Bladder
- Stores water
- Stores water
- Ureter
- Tubes in which urine flows from kidney to bladder
- Tubes in which urine flows from kidney to bladder
- Osmoregulation: Maintaining the right
level of water and absobed substances.
- Ammonia: toxic. Converted into urea or uric acid
- Urea: Combined ammonia and Co2 in liver.
- Advantage: Very low toxicity
- Extra water must be available to dissolve and get rid of it.
- Advantage: Very low toxicity
- Uric Acid: Paste, not a lot of water needed
- Urea: Combined ammonia and Co2 in liver.
- Nephrons
- Tiny filtering structures
- About a million in each kidney
- !. Glomerulus: Porous capillaries. Starting point.
High pressure squeezes out filatre
- Filtrate: water, urea and smaller ions and molecules
- Filtrate: water, urea and smaller ions and molecules
- 2. Bowman's Capsule
- 3. First Tubule:. Osmoregulation takes place. Reabsorb water and materials.
- 4. Loop of Henle: Reabsorption. Three jobs.
- 1. Extracts most of the water that we need from the filtrate.
- 2. Pumps out the salts that we want to keep
- 3. Makes medula hypertonic
- Membrane highly permeable to water
- 1. Extracts most of the water that we need from the filtrate.
- 5. Second tube. Regulates levels of potassium, sodium and calcuim
- 6. Collecting tubes: Channel excess water,
urea and other metabolic waste back to the
center of the kidney.
- Tiny filtering structures
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