| Tunica externa | |
|---|---|
 | |
 Section of a medium-sizedartery. | |
| Details | |
| Part of | Wall ofblood vessels |
| Identifiers | |
| Latin | tunica externa, tunica adventitia |
| TA98 | A12.0.00.017 |
| TA2 | 3920 |
| TH | H3.09.02.0.01009 |
| Anatomical terminology | |
Thetunica externa (Neo-Latin "outer coat"), also known as thetunica adventitia (Neo-Latin "additional coat"),[1][2] is the outermosttunica (layer) of ablood vessel, surrounding the tunica media. It is mainly composed ofcollagen 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 innertunica intima, a middletunica media, and an outer tunica externa.
The tunica externa is made fromcollagen andelastic fibers in aloose connective tissue.[1][2] This is secreted byfibroblasts.[1] 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.[3]
The tunica externa provides basic structural support toblood vessels.[1] It prevents vessels from expanding too much from internal blood pressure, particularly arteries.[2] It is also relevant in controlling vascular flow in thelungs.[1]
A common pathological disorder concerning the tunica externa isscurvy, also known asvitamin 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 andrupture, leading to a multitude of problems.[citation needed]
This article incorporates text in thepublic domain frompage 499 of the 20th edition ofGray's Anatomy(1918)
This article incorporatestext available under theCC BY 4.0 license.Betts, J Gordon; Desaix, Peter; Johnson, Eddie; Johnson, Jody E; Korol, Oksana; Kruse, Dean; Poe, Brandon; Wise, James; Womble, Mark D; Young, Kelly A (June 8, 2023).Anatomy & Physiology. Houston: OpenStax CNX. 20.1 Structure and function of blood vessels.ISBN 978-1-947172-04-3.
