The deoxygenated blood enters the right atrium via the vena cava
Blood flows through the right ventricle to the pulmonary artery which pumps deoxygenated blood the lungs
Oxygenated blood returns entering the left atrium from the lungs via the pulmonary vein
Blood flows through the left ventricle and out through the aorta pumping oxygenated blood to the rest of the body