The pulmonary orifice is located between right ventricle and pulmonary trunk, and is equipped with a valve, the pulmonary semilunar valve.The lung semilunar valve regulates the flow of blood to the pulmonary circulation . It is formed by three flaps, in the shape of a half-moon.
- front half-moon
- right and left hindquarters
The valve has a concave upper face facing the lumen of the pulmonary trunk and the inferior convex side facing the ventricle .
Also the structure of the semilunes is given by fibrous laminae coated by endocardium.These on the free margin show a nodular thickening called nodule of Morgagni . The nodules of morgagni are the analog of the nodules of Aranzio for the semilunar aortic valve.
During ventricular systole the margins of the crescents move away, while during the diastole they approach along the closing line.