The heart is a fist-sized, muscular organ that pumps blood through the body. Oxygen-poor blood enters the right atrium of the heart (via veins called the inferior vena cava and the superior vena cava). The blood is then pumped into the right ventricle and then through the pulmonary artery to the lungs, where the blood is enriched with oxygen (and loses carbon dioxide). The oxygen-rich (oxygenated) blood is then carried back to the left atrium of the heart via the pulmonary vein. The blood is then pumped to the left ventricle, then the blood is pumped through the aorta and to the rest of the body. This cycle is then repeated. Every day, the heart pumps about 2,000 gallons (7,600 liters) of blood, beating about 100,000 times.
Label the heart anatomy diagram below using the heart glossary. Note: On the diagram, the right side of the heart appears on the left side of the picture (and vice versa) because you are looking at the heart from the front.
