vein defined in 1951 yearvein - vein;
vein - (1) (Bot.). Vascular bundle of a leaf. (2) (Zool.). Bloodvessel (of fairly small diameter to distinguish it from a venous sinus) carrying blood from the minute vessels which supply tissues (the capillaries) to the heart. In vertebrates, veins have a smooth lining of flat cells (endothelium) with muscular and fibrous tissue outside; compared with arteries their walls are thin and their internal diameter large; unlike arteries and capillaries they contain simple valves which permit blood-flow only towards the heart. The pressure of blood within them is low. (3) Of insect wings, fine tubes of toughened cuticle which make a supporting framework. Contain air-tubes (tracheae) nerves and blood.
near vein in Knolik
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