Kidney Function & Failure

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  • Created by: Jo Wells
  • Created on: 28-04-13 17:53
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  • Kidney Function
    • nephrons are the filtration units in the kidneys
      • 1.ultrafiltration
        • a high pressure squeezes water, urea, ions & sugar out of the blood into the Bowman's capsule
          • membranes between the blood vessels & Bowman's capsule act like filters so big molecules (e.g.proteins) stay in the blood
      • 2.reabsorption
        • as the liquid flows along the nephron, useful substances are reabsorbed back into the blood
          • all sugar is reabsorbed (via active transport)
          • sufficient ions are reabsorbed (AT)
          • sufficient water is reabsorbed (osmosis)
      • 3. release of wastes
        • remaining substances (not reabsorbed) - urea - continue out the nephron
          • into the ureter and down to the bladder as urine
    • Kidney Failure
      • kidneys remove waste substances from the blood
        • if they don't work properly waste substances build up in the blood, causing problems (eventually death)
      • dialysis machines filter the blood
        • has to be done regularly to keep concentrations of dissolved substances in the blood at normal levels & to remove waste substances
        • a persons blood flows alongside a semi-permeable barrier surrounded by dialysis fluid
          • is permeable to water, ions and waste substances etc
            • but not big molecules (e.g.proteins)
          • fluid has the same concentration of dissolved ions and glucose as healthy blood
            • means useful dissolved ions & glucose won't be lost from the blood
            • only waste substances diffuse across the barrier
        • most patients need to have a dialysis session 3 times a week, with each session taking 3-4 hours
        • dialysis may cause blood clots or infections
      • transplanted organs
        • donor kidney can be rejected by the patient's immune system
          • the foreign antigens are attacked by the patient's antibodies
          • to help prevent this from happening, precautions are taken
            • a donor with a tissue type that closely matches the patient is chosen
              • tissue type is based on antigens (proteins on surface of most cells)
            • patient is treated with drugs that suppress the immune system


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