The pulmonary heart valve separates the right ventricle from the pulmonary artery, which transports deoxygenated blood to the lungs. As deoxygenated blood leaves the right ventricle, it passes through the pulmonary heart valve, which has been closed as the right ventricle was filling. The pulmonary heart valve opens, allowing deoxygenated blood to leave the right ventricle and flow to the lungs via the pulmonary artery. Once the right ventricle has emptied, the pulmonary heart valve closes, thereby keeping the blood from reentering the right ventricle.
From here, the blood travels through the lungs, where it is oxygenated and then returned to the left atrium. This is where the mitral heart valve is located.