Excretion

Covers Liver function, Kidney Function, Kidney failure.

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  • Excretion
    • is the removal of the unwanted products of metabolism from the body.
    • CO2 is toxic. makes blood more acidic. reduces oxygen transport.
      • is the removal of the unwanted products of metabolism from the body.
    • Urea is  toxic. amino group from the amino acid is very soluble and highly toxic. Urea is less soluble and less toxic. It is formed from ammonia and carbon dioxide.
      • Liver has many metabolic functions, have kupffer cells within the sinusoids. Also produce Bile in the bile canaliculus.
        • Detoxification of alcohol. Broken down by ethanol dehydrogenase.
          • into ethanal then broken down by ethanal dehydrogenase to form ethanoic acid which is accepted by CoA which goes into respiration.
            • NAD accepts H+ ions to form reduced NAD.
              • NAD also oxidises fatty acids. If too much alcohol is consumed, there is not enough NAD in its oxidised state to break down the fatty acids. So they are deposited in the hepatocytes.
                • Continued consumption of excess amounts of alcohol can cause "fatty liver" disease. This means the hepatocytes are unable to perform their functions as efficently. Scar tissue develops. disrupting the specialised blood flow inside the kidneys.
                  • Ammonia concentration within the blood can increase causing damage to the CNS
                    • COMA OR DEATH
                  • FATGUE due to extra toxins within blood.
      • Excess amino acids can not be stored. They are first deaminated to produce ammonia (very soluble and toxic) and keto acid.
        • the ammonia then enters the ornithine cycle, where it is combined with CO2 to form urea and H20
    • Kidneys
      • ULTRAFILTRATION
        • afferent arteriole is bigger than efferent arteriole = hydrostatic pressure in glomerulus.
        • Fenstruations in capillaries ensure only blood plasma passes into bowman's capsule, and that blood cells and plasma proteins remain in blood.
        • Podocytes, finger like projections ensure that there are gaps between the cells for the blood plasma to pass through to become glomerular filtrate in the bowmans capsule.
        • SELECTIVE reabsorption
          • sodium ions are removed by active transport from the cells lining the proximole convuluted tubule. This reduces the concentration of Na+ ions in the cytoplasm
            • Sodium ions are transported back into the cell by facilitated diffusion, glucose and amino acids are also co transported.
              • As glucose and amino acid concentration rises inside the cell cytoplasm, the   molecules diffuse into the tissue fluid and then into the blood.
          • WATER  REABSORPTION
            • LOOP of henle = hairpin countercurrentmultiplier. Water potential become more negative in the descending loop. then become less negative in ascending loop as loses salt but not H20
              • Fluid at top of Distal convoluted tubule has high water potential. Amount of water reabsorbed depends on permeability of collecting ducts.
                • OSMOREGULATION is the control of water and salt levels within the body.
                  • the permeability of the collecting duct wall is dependant on the amount of ADH (anti diuretic hormone) present in blood.
                    • water potential is measured by osmoreceptors in hypthalamus of the brain. when water potential is low the cells cells shrink and stimulate neurosecretory cells.
                      • when the neurosecretory cells are stimulated action potential is sent down axon to posterior pituitary gland and ADH is released.
                        • ADH binds to receptors on plasma membrane of cells of collecting duct. Causes a chain of enzyme controlled reactions. Aqauporins bind to plasma membrane. making collecting duct more permeable.#
      • KIDNEY FAILURE
        • CAUSES = DIABETES, HYPERTENSION, INFECTION.
        • Dialysis removes waste, excess fluid and salt from blood by passing blood over partially permeable membrane and dialysis fluid.
          • counter current to provide largest concentration gradient.
        • Kidney transplants have high survival rates. quality of life better. tissue rejection is prevented by immunodepressent drugs
          • limited by availability of good tissue match and donors.
    • URINE
      • pregnancy testing. tests for hCG hormone
        • work with monoclonal antibodies. if hormone is present hormone-antibody complex forms and moves up stick to test region. immbolised antibodies with dye bind to hormone in test region.colourbuilds up. two lines = postive test.
      • anabolic steriods increase protein synthesis within cells

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