Which tunic of an artery contains endothelium?
There are three layers in arterial wall: tunica externa, tunica media and tunica interna. Last one is inner most and contains endothelium.
Tunica externa, tunica media, and tunica interna are three tissue layers in the wall of blood vessels. In arterial wall, tunica media is thicker (compared to the wall of vein), endowed with smooth muscles.
Endothelium is the inner most lining of a blood vessel, a part of tunica interna. Endothelium is specialised squamous epithelium.
Only tissue that surrounds the capillary blood vessel is endothelium. Arround capillaries, endothelium show fenestration(pore) for allowing passage(diapedesis) of WBCs from blood to tissue space.
Cross section of an artery could be seen in this diagram: