The heart has four chambers which are the left and right atria and the left and right ventricles. There are two coronary arteries that line the surface. The right coronary artery lies between the right atrium and the right ventricle. It swings around the back of the heart like a crown. This artery divides into two large branches. The left coronary artery is larger than the right coronary artery and runs between the right atrium and ventricle. Then it divides into two branches: the descending and the transverse arteries. The heart is about the size of your fist and weighs less than a pound. The heart is located between the lungs and attached to the breast bone. An adult's heart is five inches long and three and a half inches wide.
HOW IT WORKS
Your can't control your heart. It works automatically by beating and is called an involuntary muscle. Flaps in the heart valves allow the blood to flow in only one direction. The heart makes a sound like "lub-dub"; that sound is the closing of the valves. The "lub" is the small push and the "dub" is the big push. The heart beats because of electric impulses. The heart beats about once a second. If you're in surgery and doctors are working on your heart, they put you on a special machine that pumps your blood for you like a robotic heart until the surgery is done. They do this because your heart can't beat when they're doing surgery on it. If you watch your heart in motion you will see it fill up like a balloon and then shrink. That's the blood being pumped out. The aorta is the biggest and most vital artery in the human body. It takes blood that is pumped out of the heart to the rest of the circulatory system. It comes out of the left ventricle. Blood is stopped from reentering the ventricle by aortic valves which are at the junction of the aorta and the ventricle. The aorta goes down the spine to the level of the lumbar vertebrae in the lower back.. There it divides into the common iliac arteries which give blood to the legs. Doctors like to take peoples blood pressures and do other tests on the aorta because they tell alot of information about the heart.
Diseases are common in elderly people. They are caused by a number things like a broken valve and high blood pressure. Fatty foods can cause heart disease and coronary artery disease. The more you eat healthy foods and the more you exercise, the more your body will feel good. Best of all your heart will feel strong!
"Body Works." Vers. 4.0. Softkey International, Inc., 1993
"Heart," Microsoft Encarta '95. Edition 95, Microsoft Corp. 1992-1994