Veins

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vein / vān/ • n. 1. any of the tubes forming part of the blood circulation system of the body, carrying in most cases oxygen-depleted blood toward the heart. Compare with artery. ∎  (in general and figurative use) a blood vessel: he felt the adrenaline course through his veins. ∎  (in plants) a slender rib running through a leaf or bract, typically dividing or branching, and containing a vascular bundle. ∎  (in insects) a hardened branching rib that forms part of the supporting framework of a wing, consisting of an extension of the tracheal system; a nervure. ∎  a streak or stripe of a different color in wood, marble, cheese, etc. ∎  a fracture in rock containing a deposit of minerals or ore and typically having an extensive course underground. ∎  subsurface water, esp. as considered a source or potential source of water for a well or wells and thought of as flowing in a channel. ∎ fig. a source of a specified quality or other abstract resource: he managed to tap into the thick vein of discontent to his own advantage. 2. [in sing.] a distinctive quality, style, or tendency: he closes his article in a somewhat humorous vein. DERIVATIVES: vein·less adj.vein·let / -lit/ n.vein·like / -ˌlīk/ adj. & adv.vein·y adj. (vein·i·er , vein·i·est ) .

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vein, blood vessel that returns blood to the heart. Except for the pulmonary vein, which carries oxygenated blood from the lungs to the heart, veins carry deoxygenated blood. The oxygen-depleted blood passes from the capillaries to the venules (small veins). The venules feed into larger veins, which eventually merge into the superior and inferior vena cavae, large vessels that consolidate the blood flow from the head, neck, and arms and from the trunk and legs, respectively (see also circulatory system). The vena cavae direct the blood back into the heart. The walls of a vein are formed of three layers like the walls of an artery. However, these layers are thinner and less muscular and collapse when empty. With such notable exceptions as the portal system, most veins contain valves, formed by pouches in their inner coats, that keep the blood from flowing backward. Valves are most numerous in the veins of the extremities, and are absent in the smallest veins. Veins are subject to inflammation, dilatation or enlargement (as in a varicose vein), rupture, and blockage by blood clots (thrombosis).

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vein
1. A blood vessel that carries blood towards the heart. Most veins carry deoxygenated blood (the pulmonary vein is an exception). The largest veins are fed by smaller ones, which are formed by the merger of venules. Veins have thin walls and a relatively large internal diameter. Valves within the veins ensure that the flow of blood is always towards the heart. Compare artery.

2. A vascular bundle in a leaf (see venation).

3. Any of the tubes of chitin that strengthen an insect's wing.

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vein In mammals, vessel that carries deoxygenated blood to the heart. An exception is the pulmonary vein, which carries oxygenated blood from the lungs to the left upper chamber of the heart. See also artery; vena cava

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vein
A. tubular vessel in which blood is conveyed through the animal body XIII (of a leaf XVI);

B. †small channel through which water flows XIII; line of deposit of mineral or earthy matter XIV;

C. strain of some quality; characteristic style; personal disposition; mood XVI. — (O)F. veine :- L. vēna.
Hence veiny (-Y1) XVI.

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vein (vayn) n. a blood vessel conveying blood towards the heart. All veins except the pulmonary vein carry deoxygenated blood from the tissues to the vena cava. Veins contain valves that assist the flow of blood back to the heart. (See illustrations.) Anatomical name: vena.
venous (vee-nŭs) adj.

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jugular vein In vertebrates, one of the blood vessels that carry blood from the head to the anterior vena cava and thence to the heart.

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vein A vascular bundle, or group of vascular bundles lying parallel to one another and very close together, in a leaf.

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jugular vein A paired vein in the neck of mammals that returns blood from the head to the heart. It joins the subclavian vein at the base of the neck.