At the apex of the infundibulum, the outflow tract of the right ventricle, the opening into the pulmonary trunk is closed by the pulmonary valve (Fig. 3.71), which consists of three semilunar cusps with free edges projecting upward into the lumen of the pulmonary trunk. The free superior edge of each cusp has a middle, thickened portion, the nodule of the semilunar cusp, and a thin lateral portion, the lunula of the semilunar cusp (Fig. 3.72).