Light micrograph of a section through part of the wall of a normal human elastic artery. This is a muscular artery with a thick wall that enables it to carry blood under pressure. This wall is composed of three layers. The innermost tunica intima surrounds the lumen (top). It possesses a fine elastic sheet known as the internal elastic lamina. The middle layer, the thick tunica media, is mainly composed of elastic and smooth muscle fibres (pink). The external tunica adventitia is composed of connective tissue.