Plasma or intravascular fluid makes up the
remaining 20% of extracellular fluid; this is the fluid
component of the blood and is separated from the
interstitial fluid by the capillary membrane.
There is constant movement of fluids between
compartments. Fluids can cross the cell membrane that separates intracellular fl uids from theinterstitial fl uids and can readily move through the
cell wall boundary between the interstitial fl uid
and plasma (Brooker and Nicol 2011).