AQA GCSE Biology Unit B3 Chapter 2.5 (Kidneys)

bits about kidneys.

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  • Created by: Lara
  • Created on: 20-05-10 13:21

The renal system


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Inside the kidney


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Ultrafiltration is when small molecules in the blood are filtered under high pressure into the Bowman's capsule. They then pass along the nephron. Small filtered molecules include salt, water, glucose and urea. Large molecules in the blood (e.g. proteins) and blood cells are not filtered, they stay in the blood.

Reabsorption - Urea is a toxin made from excess protein. It stays in the nephron and passes down the collectin duct in the urine to the bladder. Glucose is an important energy store. It is always reabsorbed back into the blood. Water (or salt) may be in excess or be very low in the body. If in excess it is not reabsorbed; if it is low then it is reabsorbed.

Release of wastes - The urine contains urea, no glucose (unless diabetic) and varying levels of salt and water.

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Kidney Dialysis


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How a dialysis machine works


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Kidney transplants

You have to use a donor kidney with a similar tissue type (perhaps from a relative) because similar antigens mean less chance of organ rejection.

You have to use radiation on the patient's bone marrow to decrease white blood cell production because white blood cells may "attack" the new kidney

You have to use immunosuppressant drugs that suppress the immune response to reduce the chances of rejection

After the operation, the recipient has to be kept in totally sterile conditions so decrease the chance of other infections taking hold (especially since their immune systems have been deliberately weakened)

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Kidney transplants


  • No hospital visits
  • Mobility
  • Better quality of life than if on dialysis machine


  • Have to take drugs which have side effects
  • Greater risk of infections
  • Long waiting lists
  • Moral issues
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