2 3 11 Gather Process And Analyse Information To Compare The

- People with dysfunctional kidneys are not able to remove wastes such as urea
- They have to undergo renal dialysis to regulate their blood
- The process:
o The blood is extracted from the body from a vein and passed into a dialyser, which is a bundle of hollow fibres made of a partially permeable membrane
o The dialyser is in a solution of dialysing fluid, which has similar concentrations of substances as blood
o The dialyser only allows wastes to pass through, and not blood cells and proteins. In this way it is similar to the filtrations stage of the nephron
o The wastes diffuse into the solution, and it is constantly replaced
o The anti-clotting agent, heparin, is also added to prevent clotting
o The blood is then returned to the body

Comparison of dialysis and normal kidney function

- Active and passive transport is used throughout the nephron
- Uses a series of membranes (nephrons) which are selectively permeable
- Continuous process; very efficient
- Useful substances are reabsorbed actively by the kidney
- No net accumulation of any specific ions

Renal Dialysis
- Only passive transport is used
- Also uses membranes (but artificial) which are selectively permeable
- Slow process, occurs a few times a week for patients
- Useful substances diffuse into blood from dialysing fluid, no reabsorption
- Ions such as sodium and phosphate take a while to diffuse out and can accumulate – patients should follow a specific diet