ANATOMY

Detailed explanation-1: -Tunica adventitia or tunica externa is the outer layer of the blood vessel wall. It consists of connective tissue with vasa and nervi vasorum and plays a key role in vascular health.

Detailed explanation-2: -The tunica externa (New Latin “outer coat"), also known as the tunica adventitia (New Latin “additional coat"), is the outermost tunica (layer) of a blood vessel, surrounding the tunica media. It is mainly composed of collagen and, in arteries, is supported by external elastic lamina.

Detailed explanation-3: -Collagen VI was detected in tunica media. It formed thin envelopes around SMCs. It was also positive in the ECM of pulmonary arterial adventitia.

Detailed explanation-4: -Both arteries and veins have an outer tunica adventitia layer, which contains extracellular matrix (ECM), fibroblasts and progenitor cells.