Internal auditory meatus
Encyclopedia
The internal auditory meatus (also Meatus acusticus internus, internal acoustic meatus, internal auditory canal, and internal acoustic canal) is a canal in the petrous part of the temporal bone
of the skull that carries nerves from inside the cranium towards the middle and inner ear compartments namely cranial nerve VII and cranial nerve VIII.
.
The internal acoustic meatus transmits the facial
and vestibulocochlear nerve
s 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 House who founded the House Ear Institute). The falciform, 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.
Temporal bone
The temporal bones are situated at the sides and base of the skull, and lateral to the temporal lobes of the cerebrum.The temporal bone supports that part of the face known as the temple.-Parts:The temporal bone consists of four parts:* Squama temporalis...
of the skull that carries nerves from inside the cranium towards the middle and inner ear compartments namely cranial nerve VII and cranial nerve VIII.
Structure
The opening to the internal acoustic meatus is located inside the cranial cavity, near the center of the posterior surface of the petrous 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 canalFacial canal
The facial canal is a Z-shaped canal running through the temporal bone from the internal acoustic meatus to the stylomastoid foramen. In humans it is approximately 3 centimeters long, which makes it the longest human osseous canal of a nerve...
.
The internal acoustic meatus transmits the facial
Facial nerve
The facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity...
and vestibulocochlear nerve
Vestibulocochlear nerve
The vestibulocochlear nerve is the eighth of twelve cranial nerves, and is responsible for transmitting sound and equilibrium information from the inner ear to the brain...
s and the labyrinthine artery (an internal auditory branch of the basilar artery
Basilar artery
In human anatomy, the basilar artery is one of the arteries that supplies the brain with oxygen-rich blood.The two vertebral arteries and the basilar artery are sometimes together called the vertebrobasilar system, which supplies blood to the posterior part of circle of Willis and anastomoses with...
). The facial nerve travels through the facial canal
Facial canal
The facial canal is a Z-shaped canal running through the temporal bone from the internal acoustic meatus to the stylomastoid foramen. In humans it is approximately 3 centimeters long, which makes it the longest human osseous canal of a nerve...
, eventually exiting the skull at the stylomastoid foramen
Stylomastoid foramen
Between the styloid and mastoid processes of the temporal bone is the stylomastoid foramenIt is the termination of the facial canal, and transmits the facial nerve and stylomastoid artery.- Clinical Relevance :...
.
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 House who founded the House Ear Institute). The falciform, 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.