The pulmonary valve is composed by three cusps (right, left and anterior semilunar cusps), formed by duplicatures of the lining membrane, strengthened by fibrous tissue.
They are attached, by their convex margins, to the wall of the artery, at its junction with the ventricle, their free borders being directed upward into the lumen of the vessel.
The free and attached margins of each are strengthened by tendinous fibers, and the former presents, at its middle, a thickened nodule (corpus Arantii). From this nodule tendinous fibers radiate through the segment to its attached margin, but are absent from two narrow crescentic portions, the lunulæ, placed one on either side of the nodule immediately adjoining the free margin.
Between the semilunar valves and the wall of the pulmonary artery are three pouches or sinuses (sinuses of Valsalva).