The valves found between the ventricles and blood vessels are called the semilunar valves. They are named so because the flaps forming the valves resemble half moons. The semilunar valves prevent blood from leaking from the arteries back into the ventricles when the ventricles contract.
The semilunar valves separate the ventricles from the arteries leading from them. The valve between the right ventricle and the blood vessel bringing oxygen-poor blood to the lungs, the pulmonary artery, is called the pulmonary valve. The valve between the left ventricle and the artery dispersing oxygen-rich blood throughout the body, the aorta, is called the aortic valve.