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The tunica externa (New Latin "outer coat") — also known as the tunica adventitia (New Latin "additional coat"), or adventitia for short — 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.

Tunica externa (vessels)
Blausen 0055 ArteryWallStructure.png
Illu artery.jpg
Section of a medium-sized artery.
Part ofWall of blood vessels
LatinTunica externa vasorum,
tunica adventitia vasorum
Anatomical terminology

The tunicae of blood vessels are three layers: an inner, middle, and outer layer that are called, respectively, the tunica intima, the tunica media, and the tunica externa (or tunica adventitia).


Clinical significanceEdit

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.

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See alsoEdit


This article incorporates text in the public domain from page 499 of the 20th edition of Gray's Anatomy (1918)

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