Extima

Extima (tunica adventitia, definition in system of anatomic terms: LNH (The Leningrad histologic nomenclature)) – an outside connective tissue cover lymphatic and blood vessels and some tubular bodies (preferential reproductive and secretory system).

 
Whether you know that:

Having fallen from a donkey, you more likely will kill yourself, than having fallen from a horse. Only do not try to disprove this statement.