capillary

n. very small blood vessel

adj. of or pertaining to a 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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Capillary /cap·il·lary/ 1. pertaining to or resembling a hair. 2. one of the minute vessels connecting the arterioles and venules, the walls of [more]Capillary - 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

(n.)
A tube or vessel, extremely fine or minute.
  

(n.)
A minute, thin-walled vessel; particularly one of the smallest blood vessels connecting arteries and veins, but used also for the smallest lymphatic and biliary vessels.
  

(a.)
Resembling a hair; fine; minute; very slender; having minute tubes or interspaces; having very small bore; as, the capillary vessels of animals and plants.
  

(a.)
Pertaining to capillary tubes or vessels; as, capillary action.