BV looping is a consequence of several changes:
The first dorsal fold forms an expanded primitive ventricle, referred to as the bulboventricular loop. This loop is subject to further changes, mainly of a hemodynamic nature.
Differential growth of the proximal ventricular tissue causes a counter-clockwise rotation of the folded heart tube. The site of ventricular growth marks the future left ventricle. Abnormal growth of the distal primitive ventricle causes clockwise rotation, an anomaly known as dextrocardia.
The Atrio-Ventricular (AV) canal between the primitive atrium and ventricle has now been partitioned by the fusing endocardial cushions. The division serves to direct the blood preferentially through one channel.
The development of the venous system causes an increase in right-sided venous return to the primitive atrium. Combined with the partitioning of the AV canal, the change in blood flow volume and directions assists in the outgrowth of the left ventricle.
Bulboventricular looping is essential in the establishment of normal hemodynamic patterns,
and thus normal development of septae and internal structures.