"Adventitia" comes from the Latin "adventicius" meaning "foreign, strange, extraneous, coming from abroad or from outside." Other English words that stem from "advenire" include "adventure" and "avenue."

What does Adventitia mean?

: an external chiefly connective tissue covering of an organ especially : the external coat of a blood vessel.

What are Adventitial cells?

A macrophage along a blood vessel, together with perivascular undifferentiated cells associated with it. See also: cell.