The Heart - Heart Disorders

The Heart

The heart is one part of the cardiovascular system (“cardio” means heart and “vascular” refers to blood vessels). The heart's function is to pump blood (most adults have slightly more than a gallon of blood in their bodies) through more than 60,000 miles of blood vessels. Gordon Edlin and Eric Golanty estimate that the average adult's gallon of blood contains approximately 25 trillion red blood cells, which carry oxygen from the lungs to all of the body's tissues. More than 200 million new red blood cells are produced and released each day from bone marrow into circulation. Approximately the same number of old red blood cells are removed and recycled.

The heart, a strong and highly specialized muscle a little larger than a fist, pumps blood continuously through the circulatory system. It is divided into four chambers: the two upper chambers, called atria, receive blood returning from the body via the veins; the two lower chambers, called ventricles, pump blood out of the heart into the lungs and body through the heart's main artery, the aorta. The right atrium connects to the right ventricle and the left atrium connects to the left ventricle. A thin wall between the atria and ventricles divides the heart in half. Large blood vessels lead into the atria and leave the ventricles, passing through valves that separate the atria from the ventricles and allow blood to flow in only one direction when the heart expands and contracts (beats). Each day the heart beats approximately 100,000 times, depending on the body's activity, and pumps about 2,000 gallons of blood.

The heart does not use oxygen and nutrients from the blood which passes through its chambers. Instead, it depends on a series of arteries found on the outside surface of the heart. These are called the coronary arteries, so named for their crown-like appearance as they branch out from the aorta girdling the outer surface of the heart.

Angina.     When the heart muscle does not get sufficient blood (and oxygen) for a given level of work, even for just a few minutes, chest discomfort called angina pectoris can develop. The pain, which radiates outward from the heart, usually subsides shortly if a person rests or uses nitroglycerine, a drug that dilates or opens blood vessels. Angina usually occurs when extra demands are placed on the heart–for instance, during periods of physical exertion or exposure to extreme cold or wind, or emotional stress or excitement. Some people also develop angina after eating a large meal, which requires increased blood flow to digest. Angina is not a heart attack, although it can be a warning sign that a person is at risk, and many people with angina never develop a heart attack.