- The circulatory system involves the heart pumping blood to the lungs for oxygenation and then distributing the oxygenated blood to the rest of the body. - Deoxygenated blood from the body enters the right atrium, goes to the right ventricle, and is pumped to the lungs via the pulmonary artery. - Oxygenated blood from the lungs enters the left atrium, goes to the left ventricle, and is pumped to the body via the aorta.