Development of the pharyngeal pouches occurs during the middle of the 9th prenatal day in Didelphis and slightly proceeds the establishment of the pharyngeal floor (McCrady 1938). Development is extremely rapid but typically mammalian in nature and by the middle of the tenth prenatal day, the head is characterized by a frontal eminence, by maxillary and mandibular processes, and by the hyoid arch (Krause and Cutts 1986). The mouth is well formed by prenatal day 11, and the oral cavity lined by stratified squamous epithelium that rests on a thin basement membrane. The lateral borders (presumptive lips) of the open mouth start to grow closed beginning at the angle of the jaws early during the 12th prenatal day. As these events occur, the lateral palatine processes unite at the midline separating oral and nasal cavities.
KeywordsParietal Cell Postnatal Period Enteroendocrine Cell Esophageal Epithelium Pyloric Gland
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