Which organ is responsible for pumping blood in the human body?

1. Lungs
2. Liver
3. Heart
4. Kidneys

The heart, a muscular organ with four chambers, pumps oxygenated blood via the systemic circuit and deoxygenated blood via the pulmonary circuit. Cardiac muscle (myocardium) contracts rhythmically due to sinoatrial node impulses, ensuring continuous circulation. Heart health is vital, with diseases like atherosclerosis being leading global causes of death.