Embryonic head posture and palatal shelf elevation

During embryonic and fetal stages of human development, elongation and straightening of the neck occurs. Authors have suggested that the resulting change in head posture lifts the lower border of the mandible from the pericardial region, so allowing jaw movements to assist the withdrawal of the tongue from between the palatal shelves. This aids elevation of the palatal processes prior to fusion. This paper reports on histological sections of 28 mm twin embryos which demonstrate that palatal elevation can take place in the absence of elongation and straightening of the neck, demonstrated by observation of existence of cephalic, pontine and cervical neural flexure of the brain.