Tunica externa

Tunica Externa

The Tunica Externa (pronounced: too-ni-ka ex-ter-na), also known as the adventitia, is the outermost layer of a blood vessel. It provides structural support and shape to the vessel.

Etymology

The term "Tunica Externa" is derived from Latin, where "tunica" means "coat" or "covering", and "externa" means "external" or "outer". Thus, the term refers to the outer covering of a blood vessel.

Structure

The Tunica Externa is primarily composed of collagen fibers, which provide strength and flexibility to the blood vessels. It also contains elastic fibers that allow the vessel to stretch and accommodate changes in blood pressure. The Tunica Externa is thicker in arteries than in veins, reflecting the higher pressures within arteries.

Function

The main function of the Tunica Externa is to provide structural support to the blood vessel and protect it from external damage. It also helps to anchor the vessel to surrounding tissues.

Related Terms

Tunica Intima: The innermost layer of a blood vessel.
Tunica Media: The middle layer of a blood vessel, composed primarily of smooth muscle cells and elastic fibers.
Artery: A blood vessel that carries blood away from the heart.
Vein: A blood vessel that carries blood towards the heart.
Collagen: A protein that provides structure and strength to tissues.
Elastic Fibers: Fibers that allow tissues to stretch and then return to their original shape.