Exploring the intricate structure of the cardiovascular system, this chapter details the flow of blood through the heart's chambers, emphasizing the dual circuits that operate concurrently in the body. From the movement of deoxygenated blood from the right atrium to the lungs for oxygenation to the delivery of oxygenated blood to tissues through the aorta, the chapter navigates the dynamic process of blood circulation. It also highlights the importance of veins in returning deoxygenated blood to the heart and the unique feeding mechanism of the heart's semilunar valves.