The pulmonary semilunar valve is located at the beginning of the |pulmonary artery|. This valve has three delicate cusps, or pockets, which permit ~blood~ flow in only one direction, allowing ~blood~ to flow out of the right ~ventricle~, but prevents it from backflowing into the ~ventricle~. When the |heart| refills, the crescent-shaped valve balloons out, sealed along the edge to prevent the ~blood~ from flowing backward. The ~bloods~ only exit from the ~ventricles~ is through the semilunar |valves|, so named for their crescent shaped cusps.
