Filtration:

Filtration is a process by which small molecules are forced to move across the semi-permeable membrane with the aid of hydrostatic (water) pressure or blood pressure.

The function of Filtration:

1. In the body of an animal blood pressure forces water and dissolved molecules to move through the semi-permeable membranes of the capillary wall cells.
2. In Filtration the pressure cannot force large molecules such as protein, to pass through the membrane pores.