A heart chamber is one of the hollow sections of the heart that alternately holds and pumps blood as part of the cardiovascular system. In humans, there are two each of two types of heart chamber for a total of four chambers, with the two atria on top and the two ventricles on the bottom. The flow of blood passes through each heart chamber and through the rest of the body in a specific order and with precise timing so that all of the tissues in the body receive oxygen.
Most beginning medical texts describe the blood flow in a very simple matter, "starting" in the heart chamber called the right atrium, although blood circulates in a cycle that does not really have a beginning or an end. From the right atrium, the blood moves into the bottom half of the heart, through the right ventricle. The right ventricle then pumps the blood into the pulmonary artery, which carries the deoxygenated blood to the lungs. Once the deoxygenated blood has passed through the capillaries in the lungs, released its load of carbon dioxide, and received its next supply of oxygen, it moves back through the pulmonary vein toward the heart again.
The next heart chamber the blood visits is called the left atrium. From there, the blood again flows to the bottom half of the heart and into the left ventricle. The left ventricle pumps the fully oxygenated blood into the artery called the aorta, to be carried and dispersed in smaller branches of arteries and eventually capillaries throughout the entire body. All over the body, tissues are then able to trade their carbon dioxide and waste products for fresh oxygen, keeping them alive and healthy. Afterward, the deoxygenated blood gets funneled into the veins and carried back toward the right atrium to repeat the cycle.
Each heart chamber is separated from its corresponding blood vessel and from its connecting chamber by a valve. When the valves are functioning correctly, they prevent backflow of blood through the heart. If a lot of blood were flowing backward and therefore not properly being pumped forward out of the heart, many problems can occur. Additionally, a structural problem in any of the heart chambers can cause serious health problems if it impedes the flow of blood, the strength of the heart itself, or the proper oxygenation of the body's tissues.