ABSTRACT
The external auditory canal (EAC) is derived from the dorsal aspect of the first branchial cleft. In the ninth gestational week, the ectodermal meatal plate descends towards the tympanic cavity and forms a plug. Around the 21st week, the EAC starts to form by canalization of this ectodermal plug, a process that completes by the 28th week. The most medial aspect of the ectodermal plug persists as the lateral epithelial layer of the tympanic membrane (TM). The neonatal EAC is short and straight with an almost horizontal TM. The inferior tympanic ring is not complete, but with progressive ossification of the EAC floor during childhood, the longer adult EAC – with a near vertical tympanic membrane – becomes evident from the age of 9 years.
