Anotated diagram of the heart (1. Aorta, 2. Left pulmonary artery, 3. Left atrium, 4. Left pulmonary veins, 5. Left ventricle, 6. Right ventricle, 7. Inferior vena cava, 8. Right atrium, 9. Right pulmonary veins, 10. Superior vena cava).
The heart is a hollow muscular organ thats purpose is to pump blood around the body. It is part of the cardiovascular system.