Apoptosis in the dorsal mesocardium will allow movement of the early heart tube within the pericardial cavity.
The first dorsal fold brings the inflow and outflow trunks in an adjacent position at the superior aspect of the developing heart. Conceptually, the primitive ventricle can be seen as a fulcrum around which the heart tube folds.
The dorsal fold forms the two pericardial sinuses and places the fibrous skeleton in a single plane.
Inflow and outflow trunks are positioned posteriorly as a result of the dorsal fold.
