Our arteries and arterioles [small arteries] must keep blood flowing to the tissues at all times, ensuring a consistent oxygen supply. One way they achieve this is to control their diameters. Narrowing (vasoconstriction) or expanding (vasodilation) the vessels enables blood to flow more slowly or faster. To control constriction endothelial cells, which line the blood vessels, communicate with surrounding smooth muscle cells, telling them to either relax or tense up. The two cells types are separated by an elastic layer of cells (shown in white, with blue nuclei), but holes in the layer allow the endothelial cells to reach through with finger-like projections. Scientists now know that these projections contain particular proteins (yellow) that can detect the blood pressure inside the vessel, convey that information to the muscle cells, and ultimately keep blood flowing to where it’s needed.
Written by Ruth Williams
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