Artery (labels) - histology slide

A sectional view of the arterial wall. On the right is the intima, topped by a layer of cells called the endothelium.The endothelium acts as a barrier to prevent certain substances from entering the vessel wall. In the center, the media is composed of smooth muscle cells and a network of fibrous proteins. The outermost layer, the adventitia, is composed of connective tissue.

Histology slide and description courtesy of National Institute of Aging as originater and nia.nih.gov as the source.