Arteries are the blood vessels which most often carry oxygen rich blood away from the heart, towards other tissues in the body. These blood vessels have a relatively thick muscular wall and can be felt pulsating at certain locations. The arteries terminate by dividing into rather small branches and are in a continuum with the veins, which carry the blood back into the heart.
The arterial wall consists of three tissue layers. The innermost layer is known as the ‘tunica intima’ and is a simple squamous epithelium. The middle layer of an arterial wall consists of smooth muscle cells and elastic fibers and is given the name, ‘tunica media’. The outermost layer of an artery is known as the ‘tunica externa’ and is composed of loose collagen fibers. This three-layer arrangement gives the artery its resilience to withstand the pressures as well as to conduct blood effectively throughout the body.
Function of the arteries:
As mentioned earlier, arteries transport oxygen rich blood except in the case of pulmonary artery and the umbilical artery. Thus, it is vital to have an efficient arterial system in order to maintain adequate functioning of various tissues and organs. If an artery becomes blocked, the blood flow beyond that point becomes depleted. This may result in tissue damage and, in case of vital organs, the damage may result in loss of life or permanent disability.
The main artery in the human arterial system is the ‘aorta’ and it arises from the heart at the site of the ‘aortic valve’. As soon as it emerges from the heart, it gives off the ‘coronary arteries’ which supply the heart muscles. As it ascends further, the thoracic part of the aorta, which remains within the chest, gives off branches that supply the brain, upper limbs, the chest and other nearby structures. As it descends, the aorta gives off branches to the chest wall, and in the abdomen it gives off two major arteries to supply the two kidneys. Further down, it gives off branches to supply the intestine and other abdominal organs before the aortic trunk divides itself into two and gives rise to the common iliac arteries to supply the lower portion of the body, including the legs.
Carotid arteries are the main arteries supplying the brain and the neck region. It divides into two at the level of the jaw and supplies blood to one-half of the face and the brain hemisphere. A complex network of arteries exists within the skull and it provides an efficient flow of blood for the brain tissues.
These require special mentioning as they supply large amounts of blood into the kidneys to not only replenish its oxygen need, but also to filter out toxic by-products as well as to regulate the blood pressure. Although relatively large diameter blood vessels supply the kidneys, they branch into tiny capillaries within the kidneys to provide an efficient filtering and excretion of by-products.
Blood supply to the lower extremities:
The abdominal aorta divides itself into two main arteries in the abdomen and these are known as common iliac arteries, and they supply the lower extremities of the body. Each common iliac artery divides itself into internal and external iliac arteries, where the external iliac artery continues towards each leg as the femoral artery. It should be mentioned that the pulse felt in the groin is due to the pulsation of the femoral artery.