Define/Explain: $(1)$ Semi-lunar valve.

(N/A) The semi-lunar valves are located at the openings between the right ventricle and the pulmonary artery,and between the left ventricle and the aorta.
These valves consist of three pocket-like flaps that open when the ventricles contract.
Their primary function is to prevent the backflow of blood into the ventricles from the pulmonary artery and the aorta during ventricular diastole (relaxation).