The body fluids

Abstract

The body fluids can be considered to be distributed between two compartments, intracellular and extracellular. The extracellular compartment can in turn be divided into a number of sub-compartments. These are: (a) the plasma (extracellular fluid within the vascular system); (b) the interstitial fluid (extracellular fluid outside the vascular system, and functionally separated from it by the capillary endothelium); and (c) transcellular fluids. Transcellular fluid can be defined as extracellular fluid which is separated from the plasma by an additional epithelial layer, as well as by the capillary endothelium. Transcellular fluids have specialized functions and include the fluid within the digestive and urinary tracts, the synovial fluid in the joints, the aqueous and vitreous humours in the eye and the cerebrospinal fluid.