SYSTEM. Located in the thorax, it lies left of the body's midline, above and in contact with the

diaphragm. It is situated immediately behind the breastbone, or sternum, and between the lungs, with its

apex tilted to the body cavity's left side. In most people the apex can be felt during each heart

contraction. At rest, the heart pumps about 59 cc (2 oz) of blood per beat and 5 l (5 qt) per minute,

compared to 120-220 cc (4-7.3 oz) per beat and 20-30 l (21-32 qt) per minute during exercise. The adult

human heart is about the size of a fist and weighs about 250-350 gm (9 oz).

Blood supplies food and oxygen to the cells of the body for their life needs and removes the waste

products of their chemical processes. It also helps to maintain a consistent body temperature, circulate

hormones, and fight infections. The brain cells are very dependent on a constant supply of oxygen. If the

circulation to the brain is stopped, death ensues shortly. Since heart attacks are the number-one cause

of death in the United States, the heart gets a great deal of attention.

The role of the heart was long considered a mystery and often given eleva

Some topics in this essay:
REGULATION HEARTBEAT, BLOOD HEART, HEART EXAMINATION, SYSTEM Located, HUMAN HEART, EVOLUTION HEART, CORONARY ARTERIES, heart muscle, , Motu Cordis, De Corde, atria ventricles, blood pumped, sa node, pulmonary artery, valves atria ventricles, heart's left, body temperature, muscle cells, blood flow, aortic valve, pulmonary artery aorta, blood pumped heart, contraction heart muscle, sound indicates closing,