extravasation (n.)

in anatomy, "a tube, duct, or conduit for conveying blood, lymph, semen, etc.," plural vasa, Latin, literally "vessel." Vas deferens (plural vasa defferentia) is from 1570s.

word-forming element meaning "outside; beyond the scope of; in addition to what is usual or expected," in classical Latin recorded only in extraordinarius, but more used in Medieval Latin and modern formations; it represents Latin extra (adv.) "on the outside, without, except," the old fem. ablative singular of exterus "outward, outside," comparative of ex "out of" (see ex-).