Morphogenesis of the cardiac outflow tract and aortic sac regions requires the progressive
immigration and integrated differentiation of cells having very divergent embryonic histories.
Mesodermal cells originating both within and beside the developing head contribute to
endocardium and myocardium. These cells, together with later arriving neural crest cells,
participate in the formation of the aorticopulmonary septum, truncal cushions, and semilunar
valves, although there is uncertainty regarding the precise contributions of each. In addition …