Tunica externa
The tunica externa — also known as the tunica adventitia, is the outermost tunica of a blood vessel, surrounding the tunica media. It is mainly composed of collagen and, in arteries, is supported by external elastic lamina. The collagen serves to anchor the blood vessel to nearby organs, giving it stability.
The three layers of the blood vessels are: an inner tunica intima, a middle tunica media, and an outer tunica externa.A common pathological disorder concerning the tunica externa is scurvy, also known as vitamin C deficiency. Scurvy occurs because vitamin C is essential for the synthesis of collagen, and without it, the faulty collagen cannot maintain the vein walls and rupture, leading to a multitude of problems.Additional images
