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Tunica externa (vessels)
	Section of a medium-sized artery.
	Transverse section through a small artery and vein of the mucous membrane of the epiglottis of a child. (Tunica adventitia is at 'a')
Latin	tunica externa vasorum, tunica adventitia vasorum
Gray's	subject #133 499

The tunica externa, also known as the tunica adventitia, is the outermost layer of a blood vessel, surrounding the tunica media. It is mainly composed of collagen. The collagen serves to anchor the blood vessel to nearby organs, giving it stability.

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 they rupture, leading to a wide multitude of problems.

[edit] Additional images

Anatomy of the arterial wall

Microphotography of arterial wall with calcified (violet colour) atherosclerotic plaque (haematoxillin & eosin stain)

[edit] See also

[edit] External links

Organology at UC Davis Circulatory/vessels/vessels7/vessels4 - "Bird, vessels (LM, High)"
adventitia at eMedicine Dictionary
Image at About.com

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.

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Contents

[edit] Pathology

[edit] Additional images

[edit] See also

[edit] External links