It is mainly composed of collagen and is supported by external elastic lamina.

Occasional nerve trunks containing several axons were observed adjacent to the external elastic lamina and often in regions were the lamina was disrupted.

Tunica media (the thickest layer in arteries): circularly arranged elastic fiber, connective tissue, polysaccharide substances, the second and third layer are separated by another thick elastic band called external elastic lamina.

The tunica media was primarily made up of smooth muscle cells and extracellular matrix proteins, the tunica adventitia was made up of collagen fibrils, an external elastic lamina, occasional nerve processes and fibroblasts.

Systemic arteries can be subdivided into two types - muscular and elastic - according to the relative compositions of elastic and muscle tissue in their tunica media as well as their size and the makeup of the internal and external elastic lamina.