Guide to Heart Disease

Heart works for many years without tiring and rests between beats. It gets a very good supply of blood so that it has a lot of energy available. It is made of a special kind of muscle that is very strong and is called cardiac muscle. It can contract quickly and strongly without getting tired. The muscle cells in the heart seem to run together so that they look like one giant cell. This allows the heart to “pull together.” The heart is made up of two halves because it is really two pumps connected together. Each pump has arteries taking blood away and veins bringing it back.
One of the pumps sends the blood to the lungs. The blood picks up oxygen there. When this blood returns to the heart, the second pump sends it out through arteries to the cells in the body. It picks up carbon dioxide, a waste product of the cells. When you cut, bleeding comes from capillaries and blood soon form clot. Sometimes people are born with blood that cannot form clot. They have a disease called hemophilia. For them even a small cut is dangerous. Each half of the heart has two kinds of chambers. There is a thin-walled chamber at the top. It is called the atrium, from the Latin word for “entrance hall.” The blood enters the atrium first. Under the atrium is a ventricle, which means “little hollow.” It has thick, muscular walls. There are four chambers in the heart : a right atrium, a right ventricle, a left atrium, and a left ventricle.
During its trip through the arteries, the blood delivers oxygen to the rest of the body. It passes to the liver. In the liver, it picks up glucose. The glucose is supplied to the body’s cells. And the body’s cells give their wastes to the blood. This exchange of materials always occurs through the capillaries. The capillaries then join into small veins, which join into larger veins, and so on. The largest veins bring the blood back to the right atrium. By now, the oxygen is all used up and the whole cycle is gone through once more.
The valves in the veins of the legs are especially important Blood must flow up the legs toward the heart, against the force of gravity, which pulls the blood downward. The valves in the veins keep the blood from falling back down. This is one reason why walking is good exercise. The working of the leg muscles keeps the blood moving in the leg veins. When a person stands a lot and has little exercise, the blood may not move fast enough. The blood may collect in the veins and cause them to swell up.
If a vein is cut, the bleeding that results can be controlled without much trouble. Blood flow from a vein is slow. And the thin walls of a vein can be easily pressed shut. But when an artery is cut, that is dangerous indeed. The blood gushes out forcefully with each heartbeat, and it is hard to close the artery’s muscular walls.

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