The outermost connective tissue covering of any organ, vessel, or other structure not covered by a serosa; instead, the covering is properly derived from without (i.e., from the surrounding connective tissue) and does not form an integral part of such organ or structure. Syn: tunica adventitia [NA], membrana adventitia(1).
Origin
[L. adventicius, coming from abroad, foreign, fr. ad, to + venio, to come]