Deoxygenated blood enters the right atrium from the body via the superior and inferior vena cava, passes through the tricuspid valve into the right ventricle, and then is pumped through the pulmonary valve into the pulmonary artery to the lungs for oxygenation. Oxygenated blood returns to the left atrium via the pulmonary veins, passes through the mitral valve into the left ventricle, and is pumped out through the aortic valve into the aorta to circulate throughout the body.