Artery and vein, light micrograph. The artery has an inner layer of endothelium and a thick wall, the tunica media, of several layers of smooth muscle. In contrast the vein is a capacitance vessel with a very thin wall of endothelium and myoepithelial cells and fibroblasts. Between these vessels is a thin capillary with a single layer of endothelial cells. Acrylic resin section. Haematoxylin-eosin stain. Magnification: x350 when printed at 10cm.