The external auditory meatus develops from the dorsal portion of the first pharyngeal cleft (Fig. 16.7A). At the beginning of the third month, epithelial cells at the bottom of the meatus proliferate, forming a solid epithelial plate, the meatal plug (Fig. 16.7B). In the seventh month, this plug dissolves and the epithelial lining of the floor of the meatus participates in formation of the definitive eardrum. Occasionally the meatal plug persists until birth, resulting in congenital deafness.
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