Elastic arteries, including the aorta and its major branches, are composed of the three basic tunics. The diagnostic characteristic of elastic arteries is the presence of numerous, fenestrated elastic sheets in the tunica media. Elastic arteries have a large lumen with a relatively thin wall compared with other arteries. Panel on the right shows the aortic wall at higher magnification. 15x, 200x
Tunica intima >
The tunica intima faces the blood. This layer is very thin compared to the thickness of the arterial wall and consists of an endothelium and underlying connective tissue. The tunica intima can only be distinguished at the higher magnification on the right.
Tunica media >
The tunica media is the thickest layer in elastic arteries and is composed of smooth muscle and fenestrated elastic sheets, which are formed by the smooth muscle cells.
Tunica adventitia >
Tunica adventitia is the outermost tunic and is composed of connective tissue.