The aortic semilunar valve is situated at the beginning of the |aorta|. This valve has three delicate cusps, or pockets, which permit ~blood~ flow only in one direction, allowing ~blood~ to flow out of the left ~ventricle~ up into the |aorta|, but prevents backflow 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 ~blood~'s only exit from the ~ventricle~ is through the semilunar |valves|, so named for their crescent shaped cusps.
