Heart is the hard-working muscular pump whose steady action sustains life. With each beat, the heart sends blood throughout the body to carry oxygen and food to all the body's cells. The rhythmic beating of the heart begins about seven months before birth. When the heart stops beating, we die unless some artificial method circulates and adds oxygen to our blood.
The heart is a large, hollow, muscular organ divided into left and right sides that pump at the same time. Veins collect blood from throughout the body and carry it to the right-side pump. That pump then sends blood to the lungs, where it picks up oxygen. The oxygenated (oxygen-rich) blood then flows to the left side of the heart, which pumps it through arteries to the rest of the body. Valves control the flow of blood through the heart. The left-side pump, which sends blood throughout the body, is larger and stronger than the right pump.
A division of the nervous system called the autonomic nervous system regulates the heart and blood vessels. The autonomic system controls body activities that are performed automatically, without conscious control. For example, the heart's rate automatically increases or decreases, depending on the body's needs. The heart pumps slowly while a person sleeps, providing relatively small amounts of oxygen to the resting body. But the heart rate can quickly speed up and greatly increase oxygen supplies when a person exercises, becomes frightened, or needs to fight or run.
Disease can strike any part of the heart. Although the death rate has fallen, disorders of the heart and blood vessels remain the leading cause of death in the United States and many other countries. The most common heart disease narrows the arteries that supply the heart itself with blood and oxygen. Deposits of fatty material gradually build up and block these arteries. If the heart receives too little oxygen, it may work poorly or even die. Damage to the heart muscle resulting from lack of oxygen is called a heart attack. A mild heart attack may force a person to lead a less active life, and a severe attack may cause death.
Medicine has made some of its most exciting advances in cardiology, the medical field that deals with diseases of the heart and blood vessels. For much of human history, doctors knew little about how the heart worked or how disease could affect the organ. In the 1900's, doctors learned to diagnose and treat many heart conditions that once meant death. Discoveries of new drugs and great progress in surgery have added years to the lives of many heart patients. Doctors have transplanted hearts and even developed machines that can temporarily do the work of the heart.
Doctors have also learned that people can take important steps to protect the health of their hearts. Most people can greatly reduce their risk of heart disease by exercising regularly, avoiding smoking, and limiting the amount of fat and calories in their diets.
Today, much research in cardiology focuses on learning more about the causes of heart disease so that much illness can be prevented. Other research seeks to reduce death and disability from heart disease through further development of new medicines and surgical techniques. For patients who have untreatable disorders, research continues into improving heart transplantation and producing an effective artificial heart.
