functions of the kidney

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  • functions of the kidney
    • removal of urea
      • when we digest proteins they become amino acids
        • used to build our own proteins
      • amino acids that we cant store are taken to the liver
        • stripped of nitrogen containing portion of the acid
          • this forms toxic ammonia
            • converted to urea
              • less toxic but still poisonous
                • passes into the blood and travels to the kidney
      • bowman's capsule and glomerulus
        • acts like a filter
        • blood vessel from glomerulus is narrower tan the one entering
          • = like putting thumb over a hose pipe
      • blood enters the glomerulus at high pressure
        • plasma is forced out through capillary walls
          • into the bowman's capsule
            • rapid exit
              • = ultrafiltration
                • removes waste wastes, nutrients and water from plasma
                  • leaves blood proteins and cells behind
    • reabsorption
      • occurs in the proximal tubule
      • 95% of water is reabsorbed from plasma
        • along with glucose, amino acids, vitamins and mineral salts
      • what happens next depends on the circumstances
        • e.g if we need to balance our salt and pH levles
      • next task remaining is water regulation
    • regulation of water levels
      • loss of water increases concentration of blood
        • could result in cells losing water by osmosis
        • hypothalamus detects rise of concentration
          • sends impulses to pituitary glands
            • = release of ADH
              • targets cells in the walls of the kidneys collecting ducts
      • specialised blood supply keeps medulla salty
        • by removing salt from urine in hoop of henle
          • collecting ducts are located in the salty medulla
      • presence of ADH
        • water passes through the walls of the collecting ducts
          • water diffuses out of the ducts into salty medulla
            • then back into the blood
              • = correct blood concentration and production of a concentrated urine
      • if too much water
        • blood can become diluted
          • risks blood and cells taking up water
            • by osmosis
              • = swelling and possibly bursting
        • under these circumstances hypothalamusmus isn't stimulated
          • pituitary doesn't produce ADH
            • water remains in the urine
              • is passed to the bladder
                • = more urination


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