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Human heart, illustration. Frontal view of a human heart. The heart is a hollow sac of muscular tissue that pumps blood around the body. The aorta (large artery, top) carries blood to the body. The heart also received deoxygenated blood back from the body and pumps it to the lungs for reoxygenating. Blood returning from the lungs is pumped into the aorta, and the cycle repeats.(KEYSTONE/SCIENCE PHOTO LIBRARY SPL/ELLA MARU STUDIO / SCIENCE PHOTO LIBRARY)