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Closure between the secondary palate and the primary palate and between the former and the nasal septum was studied in the Syrian golden hamster at light- and electron-microscopic level. Sequential changes in the epithelia before, during and after the closure of the primary and the secondary palate were described. A characteristic epithelial thickening was observed prior to epithelial fusion between the nasal septum and the secondary palatal shelf. Fusion of the opposing epithelia was characterized by formation of desmosomes. An unilateral or bilateral empty space was observed on each side of the epithelial seam, and it was suggested that this may represent the incisive foramen in the adult.

The morphology of musculus levator veli palatini in the 15-week fetus was analyzed using 30-micrometer subserial sections. The sample included 26 specimens, of which 9 each were sectioned coronally and sagittally while 8 were sectioned in the transverse plane. At this stage of development m. levator veli palatini takes a general attachment to the precursor of the petrous part of the temporal bone, and, in some cases, auxiliary attachments to the auditory tube complex were also observed. At its origin, the muscle is located anterior to the tube. It then runs medially, passing beneath the auditory tube prior to entering the velum. As it nears the region of the lateral pharyngeal wall, a small fascicle trails posteriorly and inferiorly to the main muscle mass and occasionally runs into the upper margin of m. constrictor pharyngis superior. The levator muscle is more localized within the velum at this stage of development than it has been reported to be in the adult, being confined here to the central third of the soft palate. Most of the fibers of the muscle appear to form a sling within the central 20% of the velum, although some were seen to take attachment to loose connective tissue and the palatine raphe. Upon its entry into the velum, m. levator veli palatini is intersected vertically by bundles of both mm. palatoglossus and palatopharyngeus.