The pulmolnary valve (PV) is a semilunar valve consisting of 3 cusps (arrow). These cusps are suspended from the pulmonary valve annulus and are separated by 3 commissures. Failure of complete separation of the commissures can lead to an inadequate cross-sectional area for ejection of right ventricular blood, resulting in obstruction due to pulmonary valve stenosis. (RA = Right atrium; TV = Tricuspid valve). Modified image used with permission from James D. St. Louis, MD.