Internal auditory meatus

Internal auditory meatus
Left temporal bone. Inner surface.
Diagrammatic view of the fundus of the right internal acoustic meatus.
Details
Identifiers
Latin	meatus acusticus internus
TA	A02.1.06.033
FMA	53163
*Anatomical terms of bone* [edit on Wikidata]

The internal auditory meatus (also meatus acusticus internus, internal acoustic meatus, internal auditory canal, internal acoustic canal, or IAC) is a canal within the petrous part of the temporal bone of the skull between the posterior cranial fossa and the inner ear.

Function

The internal auditory meatus provides a passage through which the vestibulocochlear nerve, the facial nerve, and the labyrinthine artery (an internal auditory branch of the basilar artery) can pass from inside the skull to structures of the inner ear and face.

It also contains the vestibular ganglion.

Structure

The opening to the meatus is called the porus acusticus internus, or its English translation, the internal acoustic opening. It is located inside the posterior cranial fossa of the skull, 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 internal auditory meatus 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 facial nerve travels through the facial canal, eventually exiting the skull at the stylomastoid foramen.

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.

Additional images

Internal acoustic meatus
Temporal bone at birth. Inner aspect.
Base of the skull. Upper surface.
Horizontal section through left ear; upper half of section.
The cochlea and vestibule, viewed from above.
Tympanic cavity. Facial canal. Internal carotid artery.

References

This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)

External links

Anatomy figure: 30:01-08 at Human Anatomy Online, SUNY Downstate Medical Center
cranialnerves at The Anatomy Lesson by Wesley Norman (Georgetown University) (VII)
Diagram of Porus acusticus internus
Diagram of Porus acusticus internus

The neurocranium of the skull

Occipital

Squamous part	external Inion/External occipital protuberance External occipital crest Nuchal lines planes Occipital Nuchal internal Cruciform eminence Internal occipital protuberance Sagittal sulcus Internal occipital crest Groove for transverse sinus

Lateral parts	Condyle Condyloid fossa Condylar canal Hypoglossal canal jugular Jugular process Jugular tubercle

Basilar part	Pharyngeal tubercle Clivus

Other	Foramen magnum Basion Opisthion

Parietal

Frontal

Squamous part	Frontal suture Frontal eminence external Superciliary arches Glabella foramina Supraorbital Cecum Zygomatic process internal Sagittal sulcus Frontal crest

Orbital part	Ethmoidal notch Fossa for lacrimal gland Trochlear fovea Frontal sinus Frontonasal duct

Temporal

Squamous part	Articular tubercle Suprameatal triangle Mandibular fossa Petrotympanic fissure Zygomatic process

Mastoid part	Mastoid foramen Mastoid process (Mastoid cells) Mastoid notch Occipital groove Sigmoid sulcus Mastoid antrum (Aditus)

Petrous part	Carotid canal Facial canal Hiatus Internal auditory meatus Cochlear aqueduct Stylomastoid foramen fossae Subarcuate fossa Jugular fossa canaliculi Inferior tympanic Mastoid Styloid process Petrosquamous suture (note: ossicles in petrous part, but not part of temporal bone)

Tympanic part	Suprameatal spine

Sphenoid

Surfaces	Superior surface: Sella turcica Dorsum sellae Tuberculum sellae Hypophysial fossa Posterior clinoid processes Ethmoidal spine Chiasmatic groove Middle clinoid process Petrosal process Clivus Lateral surface: Carotid groove Sphenoidal lingula Anterior surface: Sphenoidal sinuses

Great wings	foramina Rotundum Ovale Vesalii Spinosum Spine Infratemporal crest Sulcus of auditory tube

Small wings	Superior orbital fissure Anterior clinoid process Optic canal

Pterygoid processes	fossae Pterygoid Scaphoid pterygoid plates Lateral Medial Pterygoid canal Hamulus

Other	Body Sphenoidal conchae

Ethmoid

Plates	Cribriform plate Crista galli Olfactory foramina Perpendicular plate

Surfaces	Lateral surface Orbital lamina Uncinate process Medial surface Supreme nasal concha Superior nasal concha Superior meatus Middle nasal concha Middle meatus

Labyrinth	Ethmoid sinus ethmoidal foramina Posterior Anterior

Foramina of the skull (and canals, fissures, meatus, and hiatus)

Anterior cranial fossa

to Orbit:	ethmoidal foramina anterior posterior

to Nasal cavity:	olfactory foramina (CN-I) foramen cecum

Middle cranial fossa

to Orbit:	optic canal (CN-II) superior orbital fissure (CN-III,IV,V1,VI)

to Pterygopalatine fossa:	foramen rotundum (CN-V2) pterygoid canal

to Infratemporal fossa:	foramen ovale (CN-V3) foramen spinosum/carotid canal

other:	foramen lacerum hiatus for greater petrosal nerve hiatus for lesser petrosal nerve sphenoidal emissary foramen

Posterior cranial fossa

internal auditory meatus/facial canal/stylomastoid foramen (CN-VII,VIII)
jugular foramen (CN-IX,X,XI)
foramen magnum (CN-XI)
hypoglossal canal (CN-XII)
condylar canal
mastoid foramen

Orbit

to Nasal cavity:	nasolacrimal canal

to face:	supraorbital notch foramen infraorbital foramen groove zygomatic foramen -facial -temporal

to Pterygopalatine fossa:	inferior orbital fissure

other:	Inferior orbital fissure Fossa for lacrimal sac

Pterygopalatine fossa

to Nasal cavity:	sphenopalatine foramen

to Oral cavity:	greater palatine canal foramen lesser palatine canals foramina

to Infratemporal fossa:	pterygomaxillary fissure

to Nasopharynx:	palatovaginal canal

to oral cavity:	incisive canals incisive foramen

to nasal cavity:	Foramen vomerinum Meatus vomerinus Fissura vomerina Hiatus vomerinus

Other

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