Vasodilation

Vasodilation is the widening of blood vessels caused by relaxation of vascular smooth muscle. It increases vessel diameter and can alter blood flow and vascular resistance.

Vascular smooth muscle: The contractile muscle layer in blood vessel walls that regulates vessel diameter. Its relaxation directly produces vasodilation.
Thermoregulation: The regulation of body temperature through physiological processes. Skin-vessel dilation increases heat transfer from the body to its surroundings.
Blood pressure: The force exerted by circulating blood against the walls of blood vessels. Systemic dilation can reduce pressure by lowering peripheral resistance.
Angiogenesis: The formation of new blood vessels from existing vessels. It increases vascular network capacity by adding vessels, not widening existing ones.
Nitric oxide: A signaling molecule produced by endothelial cells that relaxes nearby vascular smooth muscle. It is a major signal that triggers vasodilation.
Reactive hyperemia: A temporary increase in blood flow after a period of restricted blood supply. Local dilation helps restore flow after an occlusion is removed.
Poiseuille's law: A fluid-flow relation showing how flow through a cylindrical tube depends strongly on its radius. It explains why modest diameter changes can greatly affect flow in idealized vessels.
Venous return: The flow of blood returning to the heart through the systemic veins. Changes in venous tone affect cardiac filling, unlike arteriolar dilation's main resistance effect.
Cyclic GMP: An intracellular messenger that regulates processes including smooth-muscle relaxation. Nitric oxide promotes its production, helping relax vessel walls.
Coronary circulation: The blood supply that serves the heart muscle through the coronary vessels. Coronary dilation helps match myocardial blood flow to oxygen demand.

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