The muscular organ responsible for pumping blood around the human body is the heart.
The heart is a strong muscular pump located in the chest between the lungs. It has four chambers: the right atrium, right ventricle, left atrium and left ventricle. The right side sends oxygen-poor blood to the lungs, while the left side receives oxygen-rich blood and pushes it through the aorta to the rest of the body.
Heart valves act like one-way doors, helping blood move in the correct direction. Electrical signals produced by specialised cells coordinate each heartbeat; the sinoatrial node normally sets the rhythm. During systole, the ventricles contract and eject blood. During diastole, they relax and refill.
A common mix-up is thinking the heart oxygenates blood. The lungs perform gas exchange; the heart circulates the blood between the lungs and body. The heart muscle itself also needs oxygen, supplied by the coronary arteries.