Small Muscular Artery
Small Muscular Artery

Small Muscular Artery

As muscular arteries branch and decrease in size, the number of layers of smooth muscle cells in the tunica media decreases. Also, the internal and external elastic laminae become much less prominent. Which cells sense increase blood flow and trigger smooth muscle cells to relax? Which molecule is responsible for relaxing smooth muscle?
Answer: Endothelial cells sense the rate of blood flow. When blood flow increases, endothelial cells release nitric oxide that causes smooth muscle cells to relax and increase the diameter of the vessel.