The document provides information about the structure and function of the human heart. It discusses the heart's four chambers, including the right and left atria and ventricles. It also describes the heart's four valves - tricuspid, pulmonary, mitral, and aortic - which control blood flow and prevent backflow. The document explains that the heart pumps deoxygenated blood to the lungs and oxygenated blood to the rest of the body in distinct circulations, and that its contraction and relaxation cycles pump blood out of the chambers and allow them to fill.