The Human Heart
The human heart has four chambers. On each side of the heart there is one atrium and one ventricle, thus referred to as the left atrium, left ventricle, right atrium and right ventricle. To ensure that blood does not flow backwards, the heart uses several valves, limited in movement by the papillary muscle. The mitral and tricuspid valves are what allow blood to flow from the atria to the ventricles but not in the other direction. The tricuspid does this for the right side and the mitral for the left. The other two valves work for the ventricles. The pulmonary valve makes sure blood continues in a forward motion through the pulmonary arteries and out of the heart. The aortic valve works for the left ventricle and also guarantees that blood stays on a forward path out of the heart. However, the blood leaving each of these places has a very different destination, to be discussed later. The final component of the heart is the septum. The septum, from the Latin "saeptum," meaning a dividing wall or enclosure, does just that; it divides the right and left sides of the heart so the blood does not mix. As mentioned above, there are two sides of the heart; a right side and a left side. Each side has a corresponding atrium and ventricle. The right atrium gathers de-oxygenated blood from the upper body/brain and the lower body by means of the superior (upper body) and inferior (lower body) vena cava. The oxygen-poor blood then travels through the tricuspid valve to the right atrium, where it is pumped through the pulmonary arteries to the lungs. This is called pulmonary circulation. Once in the lungs, the blood undergoes a gas exchange by receiving oxygen and leaving behind carbon dioxide. Now, the oxygenated blood travels through the pulmonary veins to the left side of the heart. The blood is pumped into the left atrium which propels it into the left ventricle after it passes through the mitral valve. When the left ventricle becomes filled with oxygen...
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