7. Effect of Kidney Failure on Human Health

§ Kidneys are excretory organs that remove mainly nitrogenous waste products (urea, creatinine), excess water and mineral salts in the form of urine.

§ Kidneys act as osmoregulators and they help to maintain the water potential of blood plasma.

§ In the event of kidney failure, patient needs to either go for kidney transplant or undergo dialysis treatment.

Mechanics of a dialysis machine.

§ Blood is drawn from the patient’s vein and it is pumped through the dialysis tubing in the dialysis machine. Tubing containing blood is bathed in a dialysis fluid.

§ The dialysis tubing being partially permeable, allows some substances to pass through. The dialysis fluid contains the same concentration of essential substances (glucose, amino acids, salts) in blood plasma and it only allows excess glucose, amino acids and salts to diffuse out of blood into the dialysis fluid.

§ Blood cells, eg red blood cells, white blood cells and platelets are too large to diffuse out of dialysis tubing.

§ Dialysis fluid does not contain nitrogenous waste and thus nitrogenous waste (urea, creatinine) found in blood diffuse out of dialysis tubing into the dialysis fluid.

§ Dialysis fluid is frequently replaced and this maintains a steep concentration gradient for exchange of substances between the blood and the dialysis fluid.

§ Flow of dialysis fluid is opposite to the flow of blood and this maintains the concentration gradient for removal of waste products.

§ Blood that is filtered is returned to the patient’s vein.