vasodilation
Sign in to savethumb|254x254px|Normal blood vessel (left) vs. vasodilation (right) Vasodilation, also known as vasorelaxation, is 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. Blood vessel walls are composed of endothelial tissue and a basal membrane lining the lumen of the vessel, concentric smooth muscle layers on top of endothelial tissue, and an adventitia over the smooth muscle layers. Relaxation of the smooth muscle layer allows the blood vessel to dilate, as it is held
Article
16 sectionsContents
- Function
- Immune system
- Mechanism
- Smooth muscle physiology
- Causes
- Endogenous
- Autonomic nervous system control
- Cold-induced
- Miscellaneous
- Treatment
- Direct vasodilation drugs
- Alpha-2A adrenergic receptor agonists
- Blood vessel muscle relaxants
- Therapeutic applications
- See also
- References
thumb|254x254px|Normal blood vessel (left) vs. vasodilation (right) Vasodilation, also known as vasorelaxation, is 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. Blood vessel walls are composed of endothelial tissue and a basal membrane lining the lumen of the vessel, concentric smooth muscle layers on top of endothelial tissue, and an adventitia over the smooth muscle layers. Relaxation of the smooth muscle layer allows the blood vessel to dilate, as it is held in a semi-constricted state by sympathetic nervous system activity. Vasodilation 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 and increase in cardiac output. Vascular resistance is the amount of force circulating blood must overcome in order to allow perfusion of body tissues. Narrow vessels create more vascular resistance, while dilated vessels decrease vascular resistance. Vasodilation acts to increase cardiac output by decreasing afterload, −one of the four determinants of cardiac output.