More about the heart

Your heart weighs well under a pound and is only a little larger than your fist, but it is a powerful, long-working, hard-working organ that is a special type of muscle. Its job is to pump blood to the lungs and to all the body tissues.

The heart is a hollow organ. Its tough, muscular wall (myocardium) is lined by a thin, strong membrane (endocardium) and is surrounded by a fibrous bag (pericardium). A wall (septum) divides the heart cavity down the middle into a "right side" and a "left side." Each side of the heart is divided again into an upper chamber (atrium) and a lower chamber (ventricle). Valves regulate the flow of blood through the heart and to the pulmonary artery and the aorta.

The heart is really a double pump. One pump (the right side) receives blood that has just come from the body after delivering nutrients and oxygen to the body tissues. It pumps this dark, bluish blood to the lungs where the blood gets rid of a waste gas (carbon dioxide) and picks up a fresh supply of oxygen which turns it bright red again. The second pump (the left heart) receives this "reconditioned" blood from the lungs and pumps it out through the aorta to be distributed by smaller arteries to all parts of the body.

For detailed information, see the article published in the fall 1999 issue of The Child's Doctor, a Children's Memorial Hospital publication for physicians who care for children.