Final answer:
Peritoneal dialysis uses the patient's peritoneal membrane as a semipermeable barrier through which urea can pass but red blood cells cannot. The semipermeable membrane in dialysis machines separates harmful substances like urea from the blood through diffusion.
Step-by-step explanation:
Peritoneal dialysis is different from hemodialysis in that peritoneal dialysis uses the patient's own semipermeable membrane, which is the peritoneal membrane. In the context of dialysis machines used by patients with kidney illnesses, a semipermeable membrane is used to separate the blood from the dialysate. The semipermeable membrane is likely permeable to urea but impermeable to red blood cells. Therefore, the correct answer to the question is d. urea, red blood cells.
Dialysis is the process that uses a semipermeable membrane with pores large enough to allow small solute molecules and solvent molecules to pass through, but not large solute molecules such as proteins or blood cells. In hemodialysis, this principle is applied using artificial kidney machines where the patient's blood flows through cellophane tubes that act as the semipermeable membrane. The concentration difference between the blood and the dialysate across the membrane facilitates the diffusion of wastes such as urea out of the blood while keeping larger components like red blood cells within the blood circuit.