Final answer:
The pressure difference across the membrane in a dialyzer is called osmotic pressure.
Step-by-step explanation:
The pressure difference across the membrane in a dialyzer, created by applying hydraulic pressure to the blood or dialysate compartment, is called osmotic pressure.
Osmotic pressure is the net pressure that drives the movement of fluid from an area higher in solute concentration (and lower in water concentration) to an area higher in water concentration (and lower in solute concentration) across a semipermeable membrane. In the context of dialysis, the osmotic pressure of the blood forces water and waste molecules through the semipermeable membrane into the dialysate.
Furthermore, osmotic pressure is determined by osmotic concentration gradients, which refer to the difference in the solute-to-water concentrations in the blood and tissue fluid. The higher concentration of solutes in one compartment creates an osmotic pressure that draws water across the membrane from the compartment with higher water concentration and lower solute concentration.