The adult body has some 60,000 miles of blood vessels that supply oxygen and other nutrients to every cell and carry away carbon dioxide and other wastes. The heart, on of nature's most durable pumps, constantly circulates 8 to 10 pints of blood through this vast network. On a typical day, the heart beats more than 100,000 times, pumping out 2,600 gallons of blood. This adds up to more than 2.5 billion heartbeats over an average lifetime, with never more than a fraction of a second's rest between each beat.
With each beat, the heart forces two or three ounces of blood into the aorta, the body's largest artery, with enough pressure to carry it to the tiniest, most distant blood vessel. As blood is depleted of its oxygen, it flows into the venous system, which carries it back to the heart and lungs to begin the cycle anew.
The heart's four chambers are separated by valves that keep blood moving in the right direction. Used blood flows into the right atrium, then to the right ventricle, which pumps it to the lungs. Now oxygenated blood passes from the lungs into the left atrium, then through the mitral valve into the left ventricle -- the main pumping chamber -- which forces it through the aortic valve into the aorta and general circulation.
Although the heart is designed to last a lifetime, cardiovascular disease remains our leading cause of death, claiming for than 900,000 lives a year. Most of these deaths are due to heart attacks, often in the prime of life. The American Heart Association estimates that 56 million Americans suffer from a cardiovascular disorder, with high blood pressure and coronary artery disease the most prevalent.
These disorders are epidemic and world wide, concentrated mostly in developed nations. They are relatively modern phenomenon that experts attribute to a combination of lifestyle factors (for example, eating a high-fat diet, smoking, not exercising) and heredity. Increasingly, however, researchers are showing that heart attacks, strokes, and other cardiovascular events can be prevented by adopting a prudent, heart-healthy lifestyle.