A valve consists of a fold (i.e., cusp or leaflet) of the tunica intima which extend into the lumen of the vessel. In this example, two open leaflets are shown along with a third leaflet whose opening is not within the plane of the section.

Muscular Artery – has a tunica intima with a prominent internal elastic lamina and tunica media with a prominent smooth muscle component.

Medium Vein – the companion vein has less distinct layers than the artery.