Excreation

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  • Excretion
    • this is the removal of metabolic waste from the body
      • the two main types of excretion
        • exhaling or getting rid of carbon dioxide
          • produced from respiration
          • carbon dioxide is taken from respiring cells to the lungs where it is then exhaled
          • these substances can have major harmful effects on the body if not removed
            • carbon dioxide can effect the pH of  the blood due to a build up of carbonic acid that forms from a reaction between the carbon dioxide and water in your blood carbonic acid freely disassociates a H+ ion lowering the pH
            • urea can have high toxicty if it builds up
              • however ammonia is even more toxic to our bodies  so must be diluted into urea
        • weeing or getting rid of nitrogenous waste in the form of urea
          • produced form excess amino acids
          • urea is made by a process called deamination where it is then taken to the liver
          • these substances can have major harmful effects on the body if not removed
            • carbon dioxide can effect the pH of  the blood due to a build up of carbonic acid that forms from a reaction between the carbon dioxide and water in your blood carbonic acid freely disassociates a H+ ion lowering the pH
            • urea can have high toxicty if it builds up
              • however ammonia is even more toxic to our bodies  so must be diluted into urea
    • the liver
      • it is vital form many processes in the body and ensuring homeostasis is maintained
      • the main blood supply for the liver is provided by the hepatic vein and artery
      • the liver has many chambers that surround the portal vein these chambers  are further subdivide into lobes these lobes have veins running along side them
      • this is the structure of a live loubel http://www.daviddarling.info/images/liver_lobule.gif
      • the liver cells have many micro villi on them used to increase the surface area they carry out man incorporation metabolic unctions such as the transformation of carbohydrates and the synthesis for bile salts and colestorl
      • they also have special kampfer cells used o break down old red blood cells
      • functions of the liver
        • the liver performs man functions these are
          • the production of bile salts used to increase the surface area avilabel for enzymes to work on
          • it controls blood glucose levels, amino acid levels and lipid levels
          • the storage of vitimins A,D & B12
          • the detoxification of alcohol/ drugs
            • detoxification reaction
              • ethanol in alcohol is oxidized using a reducing agent called NAD
                • the ethanol becomes ethnal and the NAD becomes reduced NAD
                  • the ethanal id then further oxidized to become ethanoic acid again by NAD which becomes reduced NAD
          • breakdown of hormones and the destruction of red blood cells
        • deamination is the addition of oxygen to a amino acid this breaks it down into ammonia and keto acid
    • the kidney
      • the kidneys job is to make urine while filtering out any extra nutrients
      • the kidney has a outer capsule this surrounds the cortex of the kidney below the renal cortex iis the renal medulla which is connected to the renal pelvis
        • nephrons which are responsible for making urine run through both the cortex and medulla
      • the nephron
        • the nephron starts with a blood vessel that enters a capsula know as the bowmans capsule the blood vessel then knots up
          • the shape of the capsule causes the blood to come in under high pressure this forces the micro molecules that are under 69,000 micrometers out of the blood stream and into the bowman casual
            • the micro molecules must then pass through the basement membrane in the bowmans capsule it then travels through the epithelium of the bowman's capsule and past podocytes
        • from the bowman's capsule the macromolecules now called golumura filtrate then past into the proximal convoluted tubule
          • this has a brush border of cells that have villi and microvilli that increase the surface area
            • at this point several different things happen salt ions are taken out of the glomerular filtrate via diffusion going from high conc to low con down their diffusion gradient when they enter the cell they act as a cotransporter taking glucose with them
              • the sodium is then put back into the bloodstream using a sodium potassium pump that uses ATP  glucose enters the bloodstream via diffusion
            • water enters the  cell vias osmosis  going form high water potential to low water potential down the water potential gradient
        • the loop of henle
          • from the bowman's capsule the macromolecules now called golumura filtrate then past into the proximal convoluted tubule
            • this has a brush border of cells that have villi and microvilli that increase the surface area
              • at this point several different things happen salt ions are taken out of the glomerular filtrate via diffusion going from high conc to low con down their diffusion gradient when they enter the cell they act as a cotransporter taking glucose with them
                • the sodium is then put back into the bloodstream using a sodium potassium pump that uses ATP  glucose enters the bloodstream via diffusion
              • water enters the  cell vias osmosis  going form high water potential to low water potential down the water potential gradient
          • this is used to extract any excess water from the nephron
            • water is exstracted by a counter current multiplyer
              • this works like this salt ions are released from the ascending limb into the surrounding tissue lowering the water potential
                • the golumear filtrate enters the descending limb some salt ions move in but water moves out of the filtrate going from high water potential to low water potential down the water potential gradient
                  • as it goes down the limb into the medulla the water potential becomes even lower the filtrate then enters the ascending limb which is impermeable to water as such salt ions are able to exit into the surrounding tissue lowering the water potential of the surrounding tissue even more
        • the distal convoluted tubule and collecting duct
          • the loop of henle
            • this is used to extract any excess water from the nephron
              • water is exstracted by a counter current multiplyer
                • this works like this salt ions are released from the ascending limb into the surrounding tissue lowering the water potential
                  • the golumear filtrate enters the descending limb some salt ions move in but water moves out of the filtrate going from high water potential to low water potential down the water potential gradient
                    • as it goes down the limb into the medulla the water potential becomes even lower the filtrate then enters the ascending limb which is impermeable to water as such salt ions are able to exit into the surrounding tissue lowering the water potential of the surrounding tissue even more
          • at this point the filtrate is now urine and heads into the collecting duct leading towards the urethra ready to be excreted
    • osmoregulation
      • the water level in our body is maintained by the liver and a hormone made in the hypothalamus and excreted in the pituitary gland called Anti Diuretic Hormone (ADH)
      • in the collecting duct their are special cells that are able to take in more water
        • when more water needs to be taken in ADH binds with receptors on these cells causing the movement of special vesicles containing water channels called aquaporins
          • these vesicles then fuse with the phospholipid bilayer putting channels in it that allow water in the water then goes through the cells and back into the blood stream
          • this is controlled by enzymes
      • the release of ADH is controlled by a negative feedback loop
        • if their is too litte water the hypotalmus stimuleates the rlease of ADH
          • this causes the water channels to open allowing more water to be reabsorbed into the blood stream
            • homeostasis restored
        • if their is too much water the hypothalamus stops stimulating the release of ADH
          • water  channels close less water reabsorbed into the blood stream
            • homeostasis restored
    • kidney failure

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