Nodules of semilunar cusps

The nodules of the semilunar cusps of the pulmonary valve are small, focal thickenings located at the center of the free edge of each pulmonary valve cusp. These nodules are described in the aortic valve but analogously present in the pulmonary valve, serve to facilitate complete coaptation of the cusps during valve closure, thereby preventing regurgitation. The nodules are composed of dense connective tissue and are part of the mature fibroelastic structure of the semilunar valves, which develops postnatally as described in the histological studies of valve development