The aortic and pulmonary valves (semilunar valves)
As explained in the description of the separation in the outflow tract region, the crease between the truncus and conus has a special meaning. Here the aortic and pulmonary valves (valvulae semilunares) arise. Involved in this are primarily the mesenchymal cushions that are created from immigrated neural crest cells. The septum of the outflow tract leads to a definitive separation of what was initially a common outflow tract. In the area of the conus-truncus-transition it delivers material for the pulmonary truncus and the aorta for the right and the left semilunar valves. In addition, in the ventral area, a new valve forms - the ventral semilunar valve for the truncus pulmonalis. In the dorsal area an additional fold also forms that develops into the dorsal semilunar valve of the aorta.