Capillaries

n. very small blood vessel

The word capillary is used to describe any very narrow tube or channel through which a fluid can pass. See capillary action for details.Capillaries are the smallest of a body's blood vessels, measuring 5-10 μm, which connect arterioles and venules, and are important for the interchange of oxygen, carbon dioxide, and other substances between blood and tissue cells.
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Capillaries The smallest arteries which, in the lung, are located next to the alveoli so that they can pick up oxygen from inhaled air. [more]Capillaries - Community and Resources

Noun
1. a tube of small internal diameter; holds liquid by capillary action
(synonym) capillary tube, capillary tubing
(hypernym) tube, tubing
(part-holonym) thermometer
2. any of the minute blood vessels connecting arterioles with venules
(synonym) capillary vessel
(hypernym) blood vessel
(hyponym) glomerulus
Adjective
1. of or relating to hair
(pertainym) hair
2. long and slender with a very small internal diameter; "a capillary tube"
(synonym) hairlike
(similar) thin

Capillaries are tiny blood vessels that distribute blood from arteries to the tissues of the body. They are part of the circulatory system. When pink areas of skin are compressed this causes blanching. This occurs because blood is pressed out of the capillaries. (see blood).