The tunica media (Neo-Latin "middle coat"), or media for short, is the middle tunica (layer) of an artery or vein.
Artery
The tunica media is made up of
smooth muscle cells,
elastic tissue and
collagen. It lies between the
tunica intima on the inside and the
tunica externa on the outside.
The middle coat (tunica media) is distinguished from the inner (tunica intima) by its color and by the transverse arrangement of its fibers.
-
In the smaller arteries, it consists principally of smooth muscle fibers in fine bundles, arranged in lamellae and disposed circularly around the vessel. These lamellae vary in number according to the size of the vessel; the smallest arteries having only a single layer,
-
In the larger arteries, as the iliac, Femoral artery, and carotid, elastic fibers and collagen
-
In the largest arteries, as the aorta
[ - "Aorta"] and brachiocephalic, the amount of elastic tissue is considerable; in these vessels a few bundles of white connective tissue also have been found in the middle coat. The muscle fiber cells are arranged in 5 to 7 layers of circular and longitudinal smooth muscle with about 50μ in length and contain well-marked, rod-shaped cell nucleus, which are often slightly curved. Separating the tunica media from the outer tunica externa in larger arteries is the external elastic membrane (also called the external elastic lamina). This structure is not usually seen in smaller arteries, nor is it seen in veins.[ ]
Vein
The middle coat is composed of a thick layer of connective tissue with elastic fibers, intermixed, in some veins, with a transverse layer of muscular tissue.
The white fibrous element is in considerable excess, and the elastic fibers are in much smaller proportion in the veins than in the arteries.
==Additional images==
External links
-
- "Bird, vessels (LM, High)"
