A scanning electron microscope study of the developing rat secondary palate.

The surfaces of the developing secondary palatal shelves and palate, in Wistar strain albino rats, were examined using scanning electron microscopy. Beginning on the 16th day after insemination there was a progressive degeneration of the cell surfaces on the medial aspect of the shelves. This took the form of a loss of surface microvilli and intercellular boundaries accompanied by the appearance of clefts between the cells. Fusion of the palate was complete by the 18th day and two epithelial zones could be recognized in the soft palate. The cell surface degeneration is possibly an essential change prior to shelf fusion.