The text describes the circulation of blood through the heart and body. Deoxygenated blood is received into the right atrium, pumped into the right ventricle, and then sent to the lungs. Oxygen-rich blood then returns to the heart through the pulmonary veins and enters the left atrium before flowing into the left ventricle. The coronary veins also play a role in returning oxygen-low blood from the heart's muscles back to the right atrium. The atria are connected to the ventricles by valves, and blood flows from the right atrium into the right ventricle and from the left atrium into the left ventricle.