Etude au microscope electronique a balayage du palais secondaire en formation chez le rat.

Normal fetuses 14 to 17 days old were obtained from female Wistar rats. The palates have been studied, after dissection, by scanning electron microscopy. Palatal closure is achieved, in the median and posterior region, by the elevation of the lateral palatine processus from a ventro-medial to a horizontal position; immediately after the horizontalization, they adhere to each other. Rostrally naso-palatine canal closure takes place later; it results from an epithelial and mesenchymal outgrowth under the nasal septum. The mutual adhesivity of the free edges of the lateral processes is noticeable. The pattern of the fusion surface has been considered, elements such as exfoliated cells, filopodes and microvilli are present. Their contribution to the adherence phenomenon is discussed.