Definition of Vein
Because veins lack the muscular structure and contractile capability of arteries, they have valves that keep blood moving only in one direction, toward the heart.
The body’s largest veins are the superior vena cava and the inferior vena cava, which empty blood into the heart’s right atrium.
For further discussion of cardiovascular structure and function please see the overview section “The Cardiovascular System.”
See also ARTERY.
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