tunica adventitia

…layer of the esophagus, the tunica adventitia, is composed of loose fibrous tissue that connects the esophagus with neighbouring structures. Except during the act of swallowing, the esophagus is normally empty, and its lumen, or channel, is essentially closed by the longitudinal folds of the mucosal and submucosal layers.

The outermost coat, or tunica adventitia, is a tough layer consisting mainly of collagen fibres that act as a supportive element. The large arteries differ structurally from the medium-sized arteries in that they have a much thicker tunica media and a somewhat thicker tunica adventitia. See also cardiovascular system.

The tunica adventitia, the outermost layer, is the strongest of the three layers. It is composed of collagenous and elastic fibres. (Collagen is a connective-tissue protein.) The tunica adventitia provides a limiting barrier, protecting the vessel from overexpansion. Also characteristic of this layer is the presence…

… and an outer layer, or tunica adventitia. Each coat has a number of sublayers. The tunica intima differs from the inner layer of an artery: many veins, particularly in the arms and legs, have valves to prevent backflow of blood, and the elastic membrane lining the artery is absent in…