Figure 21.

The left panel (A) is taken from an episcopic data set prepared from a developing mouse embryo at the 15th day of development with knockout of the Furin enzyme. The aortopulmonary septum has fused with the distal cushions to produce separate intrapericardial arterial trunks. The outflow cushions themselves are also fused, but with minimal development of the proximal components, which have failed to muscularize. As a result, the arterial trunks remain supported by the right ventricle, the interventricular communication being doubly committed. This arrangement is seen postnatally in the heart with double outlet right ventricle shown in the right panel (B). It has a fibrous rather than a muscular outlet septum. The interventricular communication, opening to the right ventricle between the limbs of the septomarginal trabeculation, is doubly committed.