Tunica externa (vessels)

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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
Dorlands/Elsevier	t_22/12831733

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.

Contents 1 Pathology 2 Additional images 3 See also 4 External links

[edit] Pathology

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

Schematic view of an artery

Anatomy of the arterial wall

[edit] See also

• Adventitia
• Tunica media
• Tunica intima

[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 As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.