The tunica externa (Neo-Latin "outer coat"), also known as the tunica adventitia (Neo-Latin "additional coat"),
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
in a loose connective tissue.
This is secreted by
.
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.
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Function
The tunica externa provides basic structural support to
.
It prevents vessels from expanding too much from internal blood pressure, particularly arteries.
It is also relevant in controlling vascular flow in the
.
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
External links
-
- "Bird, vessels (LM, High)"
