What is "vasodilation"

1896, from vasopressor, from vaso-, comb. form of Latin vas "container, vessel" (see vas) + dilation.\nRelated: Vasodilator (1881).

n. dilation of the blood vessels

n. dilation of blood vessels (especially the arteries)

Vasodilation (or vasodilatation) refers to the widening of blood vessels. It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins, large arteries, and smaller arterioles. The process is the opposite of vasoconstriction, which is the narrowing of blood vessels.

When blood vessels dilate, the flow of blood is increased due to a decrease in vascular resistance. Therefore, dilation of arterial blood vessels (mainly the arterioles) decreases blood pressure. The response may be intrinsic (due to local processes in the surrounding tissue) or extrinsic (due to hormones or the nervous system). In addition, the response may be localized to a specific organ (depending on the metabolic needs of a particular tissue, as during strenuous exercise), or it may be systemic (seen throughout the entire systemic circulation).

Endogenous substances and drugs that cause vasodilation are termed vasodilators. Such vasoactivity is necessary for homeostasis (keeping the body running normally).