The blood flows through the aorta after exiting the left ventricle through the aortic valve.
The aortic semilunar valve is auscultated by placing a stethoscope next to the sternum in the second intercostal space.
The valve, along with the Pulmonary semilunar valve, prevent backflow into the ventricles. The shutting of the valve also produces the second heart sound in the (Lub-Dup) complex.
Not sure what your question is, but yes they are semilunar valves your atriaventricular valves are the bicuspid and tricuspid
It prevents blood flowing back into the heart from the arteries.
The functions of the valves are to direct the flow of blood in only one direction