Tunica media

Tunica media
Artery wall
Transverse section through a small artery and vein of the mucous membrane of the epiglottis of a child. (Tunica media is at 'm')
Latin	tunica media vasorum
Gray's	subject #133 498
MeSH	Tunica+Media
Code	TH H3.09.02.0.01007

The tunica media (or just media) ( middle coat ) is the middle layer of an artery or vein.^[1]

Artery

It is made up of smooth muscle cells and elastic tissue. 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 plain muscle fibers in fine bundles, arranged in lamellæ and disposed circularly around the vessel. These lamellæ vary in number according to the size of the vessel; the smallest arteries having only a single layer^[2], and those slightly larger three or four layers. It is to this coat that the thickness of the wall of the artery is mainly due.
• In the larger arteries, as the iliac, femoral, and carotid, elastic fibers unite to form lamellæ which alternate with the layers of muscular fibers; these lamellæ are united to one another by elastic fibers which pass between the muscular bundles, and are connected with the fenestrated membrane of the inner coat.
• In the largest arteries, as the aorta^[3] and brachiocephalic, the amount of elastic tissue is very 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 nuclei, which are often slightly curved.

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. ^[4]

The white fibrous element is in considerable excess, and the elastic fibers are in much smaller proportion in the veins than in the arteries.

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 As such, some of the information contained within it may be outdated.

Additional images

• 

  Vein

• 

  Anatomy of the arterial wall

• 

  Section of a medium-sized artery.

• 

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

See also

• Tunica adventitia
• Tunica intima

References

1. ^ Histology at BU 05102loa
2. ^ Histology at BU 21103loa
3. ^ Histology at OU 66_02 - "Aorta"
4. ^ Histology at BU 05603loa

External links

• Organology at UC Davis Circulatory/vessels/vessels7/vessels3 - "Bird, vessels (LM, High)"