Question

During dialysis, which are the substances kept at a lower concentration than in the blood?

• A. Amino acid and glucose
• B. Glucose and salt
• C. Glucose and urea
• D. Salt and urea

Answer 1

Answer: (D)

Salt and urea

In dialysis, a patient's blood is passed through a dialysis machine. The dialysis machine takes over the job of their kidneys, removing waste products and balancing the levels of water and salts in the blood. Hemodialysis removes wastes and water by circulating blood outside the body through an external filter, called a dialyzer, that contains a semipermeable membrane. The blood flows in one direction and the dialysate flows in the opposite. The counter-current flow of the blood and dialysate maximizes the concentration gradient of solutes between the blood and dialysate, which helps to remove more urea and creatinine from the blood. The concentrations of solutes (for example, potassium, phosphorus, and urea) are undesirably high in the blood but low or absent in the dialysis solution, and constant replacement of the dialysate ensures that the concentration of undesired solutes is kept low on this side of the membrane.

So, the correct answer is 'Salt and urea'