what valve prevents backflow of blood into the heart
semilunar valves. The valves in the heart that separate the ventricles from the arteries. The pulmonary semilunar valve separates the right ventricle from the pulmonary artery, and the aortic semilunar valve separates left ventricle from the aorta.These valves close at the end of systole, preventing the backflow of blood from arteries to ventricles, and producing the second heart sound.emilunar valves. The valves in the heart that separate the ventricles from the arteries. The pulmonary semilunar valve separates the right ventricle from the pulmonary artery, and the aortic semilunar valve separates left ventricle from the aorta.