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EXCRETION (Different type of excretion products ( Depend on an animal…

- - - - Freshwater fish->Need to prevent too much water from coming into the body from the outside. (via active tubular reabsorption of water)
      - Saltwater fish->Need to prevent too much water from leaving the body (via active tubular secretion of MgSO4)
- - - - Passing ultrafiltrate of plasma through-> endothelium of the glomerular capillary, the basement membrane, and the epithelium of Bowman’s capsule into->the space of the Bowman’s capsule.
      - Filtration Pressure
        -forces the blood through the glomeruli
        -caused by heart’s pumping action & differences in diameter of afferent
      - Sieve-like endothelium hold back the blood cells
        -> the basement membrane stops large protein molecules
        -> filtration slits hold back smaller protein molecules.
      - Podocytes = footed cells
        
        support the filtration membrane(epithelial cells)
        
        filtration slits->permit free passage of fluid filtrate into Bowman’s space.
    - - Na, glucose and amino acids are 100% reabsorbed under normal condition.
      - Energy for reabsorption->supplied by Na-K ATPase pump on the basolateral surface of the tubular cell
      - proximal tubule, 65% of the Na+ is absorbed.
        -Co-transport with glucose and amino acid utilizing a carrier.
        -Counter-transport with H+ utilizing a carrier.
        -Chloride-driven Na+ transport.
      - descending loop of Henle -> water permeable &impermeable to solutes.
      - ascending loop of Henle->25% of Na is reabsorbed in the , which is impermeable to water.
      - 10% of Na+ is reabsorbed via co-transport of Cl-.
    - - occurs at the distal tubule (regulates the K+ and NaCl concentrations of body fluids)
      - .
        Collecting duct ->carries filtrate through the-> medulla to the-> renal pelvis and reabsorbs NaCl.
      - .
        Toxic substances such as urea, uric acid, and others are eliminated
      - . Some urea & water are reabsorbed at the collecting duct.