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Excretion (Mammalian Liver (Structure: (Divided into lobes which is…

- - - - Carries oxygenated blood to the liver to use in respiration.
    - - Carries deoxygenated blood from the digestive system to the liver.
      - Rich in products of digestion.
    - - Carries blood away from the liver back to the vena cava.
    - - Carries bile from the liver to the gall bladder where it is stored.
  - - - Glycogen is stored in the cytoplasm of hepatocytes as granules.
      - Can be broken down to glucose to be released into the blood when required.
    - - Hydrogen peroxide
        
        Converted to oxygen and water by catalase.
      - Drugs
        
        Brocken down by cytochrome P450.
      - Alcohol
        
        1) Ethanol converted to ethanal by ethanol dehydrogenase.
        
        2) Ethanal converted to ethanoate by ethanal dehydrogenase.
        
        3) Ethanoate combined with coenzyme A to produce acetyl coenzyme A which enters respiration.
        
        4) NAD reduced during each dehydrogenase reaction.
    - - Deamination:
        
        Amino acid is converted to ammonia and a keto acid.
      - Ornithine cycle:
        
        1) Ammonia and carbon dioxide combine ornithine to produce citrulline.
        
        2) Citrulline is converted to arginine by the further addition of ammonia.
        
        3) Arginine is reconverted ornithine by the removal of urea.
- - - - Brings blood from renal artery.
    - - Narrow vessel that raises blood pressure.
    - - Run around the loop of Henle.
    - - Site of filtration.
  - - - Starts in the cortex, loops down into the medulla and back up into the cortex before joining the collecting duct which joins the pelvis.
      - Bowman's capsule:
        
        Surrounds glomerulus.
      - Proximal convoluted tubule:
        
        Joins the bowman's capsule and the loop of Henle.
      - Loop of Henle:
        
        Loops down into the medulla.
      - Distal convoluted tubule:
        
        Joins the loop of Henle and the collection duct.
  - - - Basement membrane:
        
        Mesh of collagen fibres and glycoproteins prevents large molecules (RMM 69,000) passing through.
      - Epithelial cells:
        
        Podocytes have major and minor projections holding them apart so fluid can pass through.
      - Endothelium of the capillary:
        
        Narrow gaps and pores allow blood plasma through.
      - Ultrafiltration: Filtration of the blood at a molecular level under pressure.
    - - Reabsorbs all sugars, most mineral ions and 85% of the fluid.
      - Cells have many microvilli.
      - 1) Sodium ions pumped out of the cells into the blood.
      - 2) Conc of sodium ions in cytoplasm decreases.
      - 3) Sodium ions diffuse in from PCT via cotransport protein carrying glucose and amino acids.
      - 4) Water moves in from PCT by osmosis.
      - 5) Glucose and amino acids diffuse into the blood and water follows.
    - - Descending limb:
        
        Water diffuses into surrounding tissue fluid.
        
        Sodium and chloride ions diffuse into tubule.
        
        Water potential falls.
      - Ascending limb:
        
        Sodium and chloride ions move out by diffusion at base and active transport at top.
        
        Walls impermeable to water.
        
        Water potential rises.
      - Reabsorption of water.
      - Haripin counter current multiplier:
        
        Increases efficiency of transfer of mineral ions from ascending to descending limb.
        
        Creates low water potential in the medulla.
        
        Water is reabsorbed as body requires.
    - - Water moves out by osmosis lowering water potential.
- - - - A measure of how much fluid passes into the nephrons each minute.
      - A low reading indicates kidney failure.
    - - Indicated filtration mechanism is damaged.
  - - - Kidney attached to blood supply and bladder.
      - Old kidney left in place.
      - Patient must take immunosuppressant drugs.
    - - Blood from artery passed into machine.
      - Heparin added to avoid clotting.
      - Dialysis fluid contains correct concs and flows in countercurrent flow.
      - Substances diffuse in and out of blood.
      - Preformed 3 times a week.
    - - A permanent tube is implanted in the abdomen.
      - Dialysis solution fills space between organs and membrane
      - Solution drained after several hours.
      - Patient able to walk around.