Ultrafiltration

A. True It depends on pore size and hydrostatic pressure gradients; colloids are larger par-ticles than crystalloids.

B. False Substances cross cellular walls by active transport or down electrochemical gra-dients; hydrostatic pressure gradients are not involved.

C. True An outward hydrostatic pressure gradient exists at the arterial end of the capil-lary.

D. True The pressure gradient across glomerular capillary walls is greater than that in other capillaries.

E. True But active secretion is also involved in the formation of CSF.