The embryo, as represented by the model, is bent upon itself, at the level of the cranial border of its umbilical orifice—that is, at the caudal end of the pericardial region; and, as a result of the bending, the general outline of the embryo, when viewed from the side, is hook-shaped.

The dorsal and longer limb of the hook is formed by the more caudal portion of the embryo—that is, the part which would lie caudal to the cranial margin of the umbilicus if the embryo were unbent.