What are blood vessels made of?

Arteries and veins are the hollow pipes that carry blood away from and back to the heart. The arteries carry blood which is under a higher pressure than that of the veins. The artery walls are therefore thicker than those of veins. Apart from this the structure of the walls of the blood vessels are very similar. The wall of an artery is essentially made up of three distinct layers although if one was to look very carefully under a microscope it would become clear that the layers themselves are made up of concentric rings which look not dissimilar to the rings of a tree stump. However for the purposes of this discussion we will keep it simple and discuss the three major layers.

The intima

The layer lining of the blood vessel is called the intima and is made up of a single layer of cells which are the fat in the middle and thin at the edges. They are supported on a basement membrane that separates this lining from what the next major liar called the media.

The media

The media is made up of a combination of elastic tissue and muscle cells. The amount of elastic tissue and muscles cells depends upon the location of the artery concerned within the body. The arteries can therefore be divided into muscular arteries and elastic arteries. For instance, in the case of the aorta in the chest, the media contains a great deal of elastic tissue further down the aorta and into the legs, the media becomes much more muscular.

The adventitia

The outermost layer of the artery is called the adventitia. It is primarily a muscular structure contained within fibres of collagen, a strong protein which is also found in tendons and ligaments. The adventitia is therefore a very important component responsible for the inherent strength of the artery.