Caudal flexion
At S6, the connecting stalk lay in a near-dorsal position and most of it was connected to the amnion. However, at S8, it lies in a caudal position. At S11, following the caudal flexion of the embryo at S10, the connecting stalk together with the allantois move ventrally. The connection towards the umbilical vesicle narrows also from the caudal region. At the same time, caudal folding results in the establishment of the hindgut. The space between the foregut and hindgut opens towards the umbilical vesicle and becomes the midgut. The caudal flexion also causes the reflection of the surface ectoderm into amnion to shift progressively more ventral.