Ventilation is an effective tool for the developmental coordination of the entire respiratory tract. Firstly, it intervenes during fetal life by means of density and incompressibility of the amniotic fluid : this double property projects sagittally the maxillae and extends its morphogenetic area to the cranial base and the cranium.
Secondly, at birth, the appearance of surface-tension at gas-liquid alveolar interface compels to secrete a
surface-active substance which prevents the pulmonary alveolar collapse and orients the facial development in an axial direction. As to the compressibility of the new ventilatory fluid, it compels to develop postural adjustments for optimizing the container-content relationship of the less armed segments of the airways.