Tunica externa

Tunica externa
Section of a medium-sized artery.
Details
Part ofWall of blood vessels
Identifiers
Latintunica externa, tunica adventitia
TA98A12.0.00.017
TA23920
THH3.09.02.0.01009
Anatomical terminology

The tunica externa (Neo-Latin "outer coat"), also known as the tunica adventitia (Neo-Latin "additional coat"), is the outermost tunica (layer) of a blood vessel, surrounding the tunica media. It is mainly composed of collagen and, in arteries, is supported by external elastic lamina. The collagen serves to anchor the blood vessel to nearby organs, giving it stability.

The three layers of the blood vessels are: an inner tunica intima, a middle tunica media, and an outer tunica externa.

Structure

The tunica externa is made from collagen and elastic fibers in a loose connective tissue. This is secreted by fibroblasts. This is normally the thickest tunic in veins and may be thicker than the tunica media in some larger arteries. The outer layers of the tunica externa are not distinct but rather blend with the surrounding connective tissue outside the vessel, helping to hold the vessel in relative position.

Function

The tunica externa provides basic structural support to blood vessels. It prevents vessels from expanding too much from internal blood pressure, particularly arteries. It is also relevant in controlling vascular flow in the lungs.

Clinical significance

A common pathological disorder concerning the tunica externa is scurvy, also known as vitamin C deficiency. Scurvy occurs because vitamin C is essential for the synthesis of collagen, and without it, the faulty collagen cannot maintain the vein walls and rupture, leading to a multitude of problems.

Additional images

See also


This page was last updated at 2024-04-18 13:44 UTC. Update now. View original page.

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