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THE ARTERIES AND VEINS: STRUCTURE OF THE ARTERIES AND VEINS

The structure of the systemic blood vessels is the same as that of the coronary arteries. The outside of the vessel is the adventitia. The middle muscular layer is called the media, and the inner layer is called the intima. The opening (lumen) of the vessels is lined with endothelium.

The blood vessels are more than just passive channels in which blood flows. They are a dynamic element of the circulatory system in their own right, and the individual layers interact in many ways. The adventitia carries the vasa vasorum (small blood vessels supplying necessary nourishment to the other layers). It also contains nerves that can signal the muscles in the media to contract. The endothelial lining of the inner layer senses and produces messages that tell the muscle layer to contract or expand. Contraction and relaxation of muscles in the media help to control blood pressure and the amount of blood distributed to the various organs. In these and other ways, the arteries and veins can have a major impact on the overall function of the body's circulation.

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Cardio & Blood