Blood Capillaries; their function and management

Basic Information
The capillary wall is formed of an endothelial layer, the basement membrane, and isolated pericytes that wrap around endothelial cells. Pericytes can regulate the lumen of the blood vessel. At rest, only 25-35% of the capillaris are active. The capillaries are not evenly distributed throughout the body (from 300-400 per mm3 in transverse striated muscles to 2500 - 3000 per mm3 in the myocardium).

Substance and gas exchange occurs at the level of the capillaries. The degree of permeability is affected by the distribution of the endothelium. There are three different types of layouts:


 * Continuous endothelium lining,
 * Fenestrated endothelium – permeable to water and small hydrophilic molecules,
 * Discontinuous endothelium – fully permeable to all plasma components

By filtering the plasma through the capillary wall, tissue fluid is formed.

Related Articles

 * Tissue Fluid