Tunica media

The tunica media (from the Latin tunica = " robe " and media "central" ) is the middle layer of the arteries and veins ( blood vessels). This layer is often referred to simply as a media. It consists of smooth muscle cells, collagen and elastic fibers. It is located between the inner tunica intima and tunica adventitia of the outboard.

Histology

The strength of the muscle layer is very different from blood vessel to blood vessel. In general, the media is in arteries particularly strongly developed and forms the strongest wall layer. In the veins the limit of three wall layers is often very blurred, while they clearly delimit in the arteries. In arteries can vary between media and tunica externa an elastic membrane, the membrana elastica externa and between media and tunica intima, the internal elastic are. This is the case for example in the aorta.

The media in arteries

In arterial tunica media that is responsible for the size of the lumen and the production of extracellular matrix. In large arteries the media is the strongest layer. The muscle fibers have the task of the pressure ( blood pressure) was recorded in the vessel and to regulate it.

Due to the high content of elastic fibers in the tunica media of elastic arteries seen macroscopically yellowish. In muscular arteries, however, the media is composed of dense and helically arranged smooth muscle cells and little elastic and collagen connective tissue.

The mean thickness of the media is in the thoracic aorta from 1.21 to 1.43 mm and in the aorta abdominalis (above the renal aorta ) from 0.35 to 0.73 mm.

The Media in veins

In principle, the structure of the tunica media in the veins of the arteries is the same, but veins have a much thinner muscle wall than arteries.

Pathology

The muscle layer in the tunica media is subject to various degenerative processes, which results in decreasing elasticity ( stiffening ) of the vessel wall, thickenings, deposits and narrowing (stenosis ) can result. This is a natural process that is caused by an age-related, reduced Regenerationssfähigkeit of the cells involved.

Thus, the tunica media plays an important role in the development of atherosclerosis. By saturating the muscle layer by increased pressure requirement especially in arterial hypertension, the muscle wall can be so strong that it even is poorly supplied with oxygen. This can lead to cell death and scarring in the muscle layer. The lumen is then strongly concentrated under circumstances that at little or no blood can flow through the affected vessel. Due to the excessively slow blood flow can in turn form thrombi and clots that can lead to vascular obstruction. Particularly affected are the arterioles and capillaries.