Small Artery

Looking at this vessel, I can visualize three layers of smooth muscle. When an artery has 3 to 25 layers of muscle in the tunica media, it is considered a small artery. Remember, the nuclei of the endothelium bulge into the lumen of these vessels because the muscle contracts during fixation.

(Virtual Microscopy for Small Artery, Arteriole and Capillaries on Capillaries page,)