The tympanic cavity, which originates in the endoderm, is derived from the first pharyngeal pouch (Figs. 16.2 and 16.7). This pouch expands in a lateral direction and comes in contact with the floor of the first pharyngeal cleft. The distal part of the pouch, the tubotympanic recess, widens and gives rise to the primitive tympanic cavity, and the proximal part remains narrow and forms the auditory tube (eustachian tube; Fig. 16.7B and 16.8), through which the tympanic cavity communicates with the nasopharynx.
Walls of central portion of outpocketing are apposed
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