capilar

Capilar is an adjective used in several Romance-language scientific vocabularies to denote relation to capillaries, the smallest blood vessels in the circulatory system. In medical and biological contexts, capilar describes anything pertaining to capillaries or to the capillary network that connects arterioles and venules. Capillaries are thin-walled vessels, typically one endothelial cell thick, with little or no smooth muscle, and they form dense networks in tissues to enable the exchange of oxygen, carbon dioxide, nutrients and wastes between blood and cells. The capillary radius is around 3–10 micrometers, allowing red blood cells to pass in single file.

In physics and chemistry, capillary action (capillary rise or capillary effect) refers to the spontaneous movement of liquids in narrow tubes or porous materials due to surface tension and adhesive forces between liquid and solid. The height to which a liquid rises in a capillary tube depends on surface tension, the contact angle, liquid density, gravity and tube radius; smaller radii produce greater rise.

In botany and plant physiology, capillary action contributes to the movement of water through narrow channels of plant tissues, particularly in the xylem. While capillarity assists transport, it operates in conjunction with transpiration pull and root pressure to move water from roots to shoots.

Etymology: capilar derives from Latin capillaris “hair-like,” from capillus “hair.” The term is commonly used in Spanish and Portuguese, with English equivalents being capillary and capillarity. See also microcirculation, capillary bed, capillary action.