ad·​ven·​ti·​tia ˌad-vən-ˈti-shə How to pronounce adventitia (audio)
: an external chiefly connective tissue covering of an organ
especially : the external coat of a blood vessel
adventitial adjective

Word History


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

Time Traveler
The first known use of adventitia was in 1854

Dictionary Entries Near adventitia

Cite this Entry

“Adventitia.” Dictionary, Merriam-Webster, Accessed 26 May. 2024.

Medical Definition


ad·​ven·​ti·​tia ˌad-vən-ˈtish-(ē-)ə How to pronounce adventitia (audio) -(ˌ)ven- How to pronounce adventitia (audio)
: 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

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