adventitia

noun

ad·​ven·​ti·​tia ˌad-vən-ˈti-shə 

-(ˌ)ven-

: an external chiefly connective tissue covering of an organ

especially : the external coat of a blood vessel

adventitial

ˌad-vən-ˈti-shəl 

-(ˌ)ven-

adjective

Word History

Etymology

borrowed from New Latin, alteration of Latin adventīcia, neuter plural of adventīcius "coming from outside, external" — more at adventitious

First Known Use

1854, in the meaning defined above

Medical Definition

adventitia

noun

ad·​ven·​ti·​tia ˌad-vən-ˈtish-(ē-)ə  -(ˌ)ven- 

: the outer layer that makes up a tubular organ or structure and especially a blood vessel, is composed of collagenous and elastic fibers, and is not covered with peritoneum

called also tunica adventitia, tunica externa