Explain the concept and mechanism of dialysis.

 

Concept of Dialysis:

• If one kidney is damaged or removed, then the other kidney alone can fulfil excretory needs. 
• However, the failure of both the kidneys allows urea and other wastes to accumulate in the blood.
• Such a patient undergoes dialysis.
• In dialysis, an artificial kidney is used.

Mechanism of Dialysis:

• The artificial kidney contains tubes made of cellophane with a semi-permeable lining.
• These tubes are suspended in a tank filled with a dialysing solution.
• This fluid contains water and glucose in concentrations similar to those in blood.
• The patient’s blood is led from the radial artery and cooled at 0°C.
• Then anticoagulant heparin is added to the blood.
• Blood is then passed through semi-permeable coiled cellophane tubes.
• The tubes allow small molecules such as urea, creatinine, uric acid to pass out.
• Also metabolic wastes are filtered out in the surrounding solution.
• But the macromolecules such as proteins are retained in the blood.
• Purified blood is then mixed with antiheparin and warmed to the body temperature.
• The purified blood is returned through a vein in the same arm.
• The function of dialysis is similar to the function of the kidney, but the only difference is there is no reabsorption during dialysis.