Pulmonary semilunar valve differs from tricuspid valve because

Chordae tendineae are tendon-like, fibrous cords that connect atrioventricular valves (bicuspid and tricuspid valves) of the heart with papillary muscles.

The semilunar (SL) valves are made up of three crescent moon–shaped cusps. Each cusp attaches to the arterial wall by its convex outer margin. The SL valves allow ejection of blood from the heart into arteries but prevent backflow of blood into the ventricles.