Degree of the contraction of vascular smooth muscle in the wall of a resistance artery is directly connected to the size of the lumen.
Quick functional changes are accomplished by contraction and relaxation of smooth muscle cells in the wall of the small arteries.
The regulation of arterial diameter and wall structure is a continuous process of adaptation to changing needs, ranging from exercise to development of the body.
This adaptation may malfunction: too small a diameter of the resistance vessels relates to insufficient tissue perfusion as well as hypertension.
Blood flow is sensed by the endothelial cells, which release factors such as nitric oxide that cause relaxation and remodeling towards larger diameters.