The origin and early development of the nasal septum in human embryos.

Based on scanning electron microscopic dissections of human embryos and fetuses of the sixth to the twelfth week (Carnegie stages 16-23 and early fetus), the origin of the nasal septum was studied. The findings show that the nasal septum does not grow downwards. It is derived from the tissue between the primary choanae: as such, its anlage is present from the very beginning. Its contact and fusion with the palatal shelves is made possible by the elevation of the palatal shelves from the vertical into the horizontal position, as the tongue descends.