Artery, << AHR tuhr ee, >> is the name of the tubes or blood vessels through which blood is pumped away from the heart to the various parts of the body. The blood carried by most arteries is bright red because it has picked up oxygen while passing through the lungs. However, the blood that flows through the arteries connecting the right side of the heart with the lungs has not yet picked up oxygen. This blood has a brownish color. If an artery is cut, blood gushes out in spurts timed with the heartbeats. Veins differ from arteries because they carry the blood back to the heart instead of away from the heart. If a vein is cut, blood flows from it in an even stream.
When a large blood vessel has been cut by accident, the difference in the color and flow of the blood from the vessel makes it possible to tell whether an artery or a vein has been injured.
The walls of arteries
are made up of three layers. The outer layer consists of elastic tissue, and the middle layer is muscle. The inner layer, or lining, of the arteries is made of thin, smooth cells of the same kind that line the other blood vessels and the heart. Each time the heart beats, the elastic walls of the arteries swell to make room for the blood forced into them. Then their muscular tissues slowly contract again. This squeezes the blood farther along the length of the arteries and toward the capillaries. In this way, the arteries do a considerable share of the work that keeps the blood circulating through the body. If the arteries had rigid instead of elastic walls, the heart would have to pump all the blood without the arteries’ assistance. As a result, the heart would work much harder than it does. This is what happens to persons who suffer from arteriosclerosis (hardening of the arteries).
Principal arteries.
The largest of all the arteries is the aorta. It is directly connected with a chamber of the heart. The heart pumps oxygenated blood through the aorta and its many branches to nearly all parts of the body. Two small but important branches of the aorta are the coronary arteries. They supply the blood by which the heart muscle itself is nourished. The right and left carotid arteries carry blood to the two sides of the head and neck. Blood flows through the right and left subclavian arteries to the shoulders and arms. Numerous other branches of the aorta furnish blood to the internal organs. In the abdominal region the aorta divides into two large branches, the right and left iliac arteries. These arteries have branches that supply the organs located in the pelvis. The iliac arteries then continue downward into the legs, where they become known as the femoral arteries.
After the arterial blood has passed through the body and has picked up impurities, the veins collect it and return it to another chamber of the heart. The heart pumps this blood through the pulmonary artery to the lungs. Here the blood takes on a new store of oxygen. It then returns to the heart, where it is once more pumped out through the aorta.
