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GCSE Biology · key term
A fluid with carefully controlled concentrations that exchanges substances with the blood during dialysis.
Used by AQA
Specification 4.5.3.3 · Paper 2
Revise: Treating Kidney Failure: Dialysis and TransplantsInside the machine, the blood and dialysis fluid flow on opposite sides of a partially permeable membrane. Blood cells and large plasma proteins remain in the blood, while small dissolved substances can cross the membrane. The treated blood is then returned to the body.
When explaining urea removal, link the facts in a chain: the dialysis fluid contains no urea, so a concentration gradient exists and urea diffuses across the partially permeable membrane from the blood into the fluid.
Do not say that dialysis fluid contains no glucose or ions. It contains normal concentrations of glucose and useful ions, preventing their net loss; excess ions can still leave the blood.
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