In the dialyzer, wastes are moved from blood into which medium?

• A. Dialysate
• B. Urine
• C. Lymph
• D. Air

Answer: (A)

Wastes move from blood into dialysate. In the dialyzer, blood flows on one side of a semipermeable membrane and dialysate on the other. Because the dialysate is formulated to have lower concentrations of waste solutes, small molecules like urea and creatinine diffuse across the membrane from blood into the dialysate, which is then carried away. This cleans the blood while the blood itself stays inside the circulatory system. Urine is produced by the kidneys, lymph is a different body fluid, and air has no role in the dialyzer.