Capillary

Capillary, minute blood vessel that connects the arteries and veins. In general, the capillaries comprise fine tubes, approximately 0.004 in (0.1 mm) in diameter, the same order of size as the red blood corpuscles. The capillary walls are one cell thick and arranged in a network throughout every tissue of the body. Here, the primary functions of the circulation—the exchange of gases, nutrients, metabolites, and heat—take place.

See also: Circulatory system.