Human heart valves, animation. The valves (red) of the heart prevent blood flowing in the wrong direction. Two valves are found between the atria and the ventricles, the tricuspid valve between the right atrium and ventricle, and the mitral valve between the left atrium and ventricle, and the two semilunar valves in the arteries leaving the heart, called the pulmonary and aortic valves, after their parent artery.