[ad-ven-tish-ee-uh, -tish-uh] 
| the external covering of an organ or other structure, derived from connective tissue, esp. the external covering of a blood vessel. |
| ad·ven·ti·tia (ād'věn-tĭsh'ə, -vən-) n. The membranous outer covering of an organ or a blood vessel. [New Latin, from Latin adventīcius, foreign; see adventitious.] ad'ven·ti'tial adj. |
adventitia ad·ven·ti·tia (ād'věn-tĭsh'ə, -vən-)
n.
The outermost membranous covering of an organ or structure, especially the outer coat of an artery.
adventitial ad·ven·ti·tial (ād'věn-tĭsh'əl, -vən-)
adj.
Of or relating to the adventitia of an organ or blood vessel.
Adventitious.
vɛnˈtɪʃ