- Gray's Anatomy and the National Heart Lung and Blood Institute (NHLBI) provide excellent, detailed descriptions of cardiac anatomy and function. The basic structure of the heart consists in two upper chambers called atria (singular: atrium) and two, larger lower chambers called ventricles. While the heart has a larger right atrium than left, it has a larger left ventricle than right. Overall, it has a larger left side. A bio-electrical conduction system regulates the speed and rhythm of the heartbeat.
- The right side of the heart receives blood returning from the rest of the body, which has used up the oxygen in the blood and filled it with carbon dioxide. The bluish blood enters the heart in the right atrium, which pushes the blood into the ventricle. The ventricle, in turn, pumps the blood to the lungs.
- In the lungs, the blood loses its carbon dioxide and picks up oxygen. The bright red blood enters the left atrium, which pumps it into the left ventricle, which then pumps the blood to the rest of the body.
The two atria push the blood into the two ventricles at the same time. In like manner, the two ventricles pump at the same time. The heartbeat consists in a "lub-DUB" in which the weaker "lub" reflects the relatively easy job of the atria to pump the blood in to the ventricles. The stronger ventricles make the stronger "DUB" sound. - Veins bring blood to the heart. The superior vena cava (meaning literally, upper hollow vein) brings blood from the upper body to the right atrium, while the inferior or lower vena cava brings blood from the lower body. On the left side, the pulmonary veins bring the oxygenated blood to the left atrium from the lungs.
- Arteries carry blood away from the heart to other parts of the body. The pulmonary arteries bring the blood from the right ventricle to the lungs. The aorta, the large artery coming off of the left ventricle, carries blood to the whole rest of the body. It branches quickly into four arteries: the brachiocephalic artery supplies the head and the right arm through its branches the right common carotid artery and the right subclavian artery; the left common carotid arterty, which supplies the head; the left subclavian artery, which supplies the left arm; and the large descending aorta, which supplies the rest of the body.
- The heart has two kinds of valves, well illustrated in the resources at AtriCure.com. The atrioventricular valves prevent backflow of blood into the atria when the ventricles pump. The tricuspid valve on the right side has three cusps, while the bicuspid or mitral valve on the left has two. For more strength, papillary muscles and chordae tendineae attach the cusps to the inside of the ventricles.
The semilunar valves prevent backflow of blood from the arteries into the ventricles when the ventricle relaxes between pumps. The aortic valve and the pulmonary valve, in the aorta and pulmonary arteries, respectively, both have three cusps. - According to information published by NY Presbyterian Hospital, the heart beats over 100,000 times a day or 42 million times a year. The heart naturally requires a consistent and strong supply of blood to keep pumping. The coronary arteries that supply the ever-hungry heart muscle with much-needed blood and nutrients come directly off of the aorta. The coronary veins collect the blood from the heart and bring it to the right atrium.
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