For the period of the systole phase, the atrioventricular valves are closed due to the contract of the right ventricle and the semilunar is opened. In the pulmonary artery, the deoxygenated blood is pumped the blood is carried to the lungs. The pulmonary valves make sure it prevents the flow of blood back into the right ventricle. In the lung, the de-oxygenated blood is oxygenated and returns to the left atrium of the heart through the pulmonary veins. For the period of the systole phase, the atrioventricular valves are closed due to the contract of the right ventricle and the semilunar is opened. In the pulmonary artery, the deoxygenated blood is pumped the blood is carried to the lungs. The pulmonary valves make sure it prevents the flow
