The organ responsible for pumping blood in the human body is the heart. This muscular organ is located in the chest cavity and functions as part of the circulatory system. The heart pumps oxygenated blood from the lungs to the rest of the body and returns deoxygenated blood back to the lungs for reoxygenation. It has four chambers: the left and right atria and the left and right ventricles, which work in unison to ensure efficient blood circulation. The heart's rhythmic contractions are vital for maintaining life and supporting all bodily functions.