Kidney dialysis

• unfiltered blood is taken from a blood vessel and is mixed with anti-coagulants (to prevent blood clotting)
• the unfiltered blood is pumped into the dialysis machine
• in the machine there’s a partially permeable membrane to separate unfiltered blood and the dialysis fluid
• the blood flows in an opposite direction to the dialysis fluid so a concentration gradient is maintained + substance exchange can occur
• dialysis fluid contains glucose, ions and no urea
• the urea can move across a partially permeable membrane down the concentration gradient and in the fluid by diffusion