The critical care nurse is providing a training session on the principles of renal replacement therapies. When discussing how solutes move across a semipermeable membrane from a higher to lower concentration, the nurse is describing:

Question

1. Ultrafiltration
2. Diffusion
3. Active transport
4. Osmosis

Answer 1

2
Rationale 1: Ultrafiltration (convection) involves a pressure gradient being created between the sides of the semipermeable membrane. Solutes are carried in solution across the semipermeable membrane in response to the pressure gradient, producing an ultrafiltrate.
Rationale 2: Diffusion involves the movement of solutes across a semipermeable membrane from a solution where they are in a higher concentration (the plasma) to a solution where they are in a lower concentration (the dialysate).
Rationale 3: Active transport (sometimes called active intake because of the absorbing movement of particles) is an energy-requiring process that moves material across a cell membrane and up the concentration gradient.
Rationale 4: Osmosis occurs when solution (water) moves from an area of low-solute concentration (the plasma) to an area of higher solute concentration (the dialysate).