adventicius = coming from abroad; outer layer of a tube.
Literally the "outer coat" or outer layer of the wall of an artery.
An outer layer of connective tissue surrounding vessels containing longitudinally arranged collagen fibers. The adventitia is continuous with more external connective tissue through which the vessel runs.
Outer layer of a blood vessel which is composed primarily of connective tissue
The tunica adventitia renamed tunica externa is the outermost layer of a blood vessel, surrounding the tunica media. It is mainly composed of collagen. The collagen serves to anchor the blood vessel to nearby organs, giving it stability.