The heart is a muscle about the size of a fist. It contracts and relaxes in order to pump blood throughout the body. The heart consists of four chambers: the right atrium, right ventricle, left atrium and left ventricle. The right side of the heart receives blood that is low in oxygen. It pumps the oxygen-depleted blood through the pulmonary arteries into the lungs where it becomes oxygen-rich. The left side of the heart receives oxygen-rich blood from the lungs and pumps blood through the aorta. Blood leaving the left side of the heart provides oxygen delivery throughout the body. After delivery, the, now oxygen-depleted, blood travels through the veins and returns to the right side of the heart. And, the cycle continues…

St. Jude's - Inside a Healthy Heart

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