Internal Auditory Meatus - Structure

Structure

The opening to the internal acoustic meatus is located inside the cranial cavity, near the center of the posterior surface of the petrous part of the temporal bone. The size varies considerably; its margins are smooth and rounded. The canal is short (about 1 cm) and runs laterally into the bone. At its end are the openings for three different canals, one of which is the facial canal.

The internal acoustic meatus transmits the facial and vestibulocochlear nerves and the labyrinthine artery (an internal auditory branch of the basilar artery). The facial nerve travels through the facial canal, eventually exiting the skull at the stylomastoid foramen.

The opening of the meatus is called the porus acusticus internus, or its English translation, the internal acoustic opening.

The antero-superior part transmits the facial nerve and nervus intermedius and is separated from the postero-superior section, which transmits the superior vestibular nerve, by Bill's bar (named by William F. House). The falciform crest or transverse crest separates the superior part from the inferior part. The cochlear nerve runs antero-inferiorly and the inferior vestibular nerve runs postero-inferiorly.

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