How the Heart Works
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Heart Chambers
The heart consists of four separate compartments, or chambers. There are two chambers on the left side of the heart and two on the right. The upper chamber on each side, known as the atria, receive and collect blood. The lower chambers, or ventricles, pump the blood to all parts of the body and are larger and thicker than the atria.
The left ventricle is the main pumping chamber, pumping blood to all parts of the body, except the lungs, while the right ventricle pumps blood exclusively to the lungs. A thick, muscular wall, the septum, divides the right and left sides of the heart and prevents blood from passing from one side to the other.