The central organ of the human circulatory system is the heart. The heart is a muscular organ responsible for pumping blood throughout the body, supplying oxygen and nutrients to tissues while removing waste products. It consists of four chambers: the right atrium and ventricle, which handle deoxygenated blood returning from the body, and the left atrium and ventricle, which distribute oxygenated blood received from the lungs. The heart works continuously, influenced by electrical signals from the sinoatrial node, regulating the heartbeat. Its vital role makes it essential for maintaining overall bodily functions and homeostasis.