The primary organ of the circulatory system is the heart. This muscular organ is responsible for pumping blood throughout the body, delivering oxygen and nutrients to tissues and removing waste products like carbon dioxide. The heart consists of four chambers: the left and right atria, and the left and right ventricles, working in tandem to maintain blood flow in two circuits—systemic and pulmonary. It is crucial to overall health, and its rhythmic contractions are regulated by electrical impulses. Proper functioning of the heart is essential for sustaining life and supporting all bodily functions.