Internal auditory meatus

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Internal auditory meatus
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Right temporal bone. Inner surface.
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Diagrammatic view of the fundus of the right internal acoustic meatus.
Details
System Petrous part of the temporal bone of the skull
Identifiers
Latin meatus acusticus internus
TA98 A02.1.06.033
TA2 671
FMA 53163
Anatomical terms of bone

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

Contents

Structure

The opening to the meatus is called the porus acusticus internus or 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 outer margins are smooth and rounded.

The canal which comprises the internal auditory meatus is short (about 1 cm) and runs laterally into the bone.

The lateral (outer) aspect of the canal is known as the fundus. [1] The fundus is subdivided by two thin crests of bone to form three separate canals, through which course the facial and vestibulocochlear nerve branches.[ citation needed ] The falciform crest first divides the meatus into superior and inferior sections; a vertical crest (Bill's bar, named by William F. House) then divides the upper passage into anterior and posterior sections. [2] Although there are three osseous canals, the fundus is conceptually divided more commonly into four quadrant areas according to the four major nerve branches of the inner ear:

The cochlear and vestibular branches of cranial nerve VIII separate according to this schema and terminate in the inner ear. The facial nerve continues traveling through the facial canal, eventually exiting the skull at the stylomastoid foramen. A common mnemonic to remember the anterior quadrants of the inner ear is: "seven up, coke down" (seventh nerve superior, cochlear nerve inferior).

Function

The internal auditory meatus provides a passage through which the vestibulocochlear nerve (CN VIII), the facial nerve (CN VII), and the labyrinthine artery (an internal auditory branch of the anterior inferior cerebellar artery in 85% of people) can pass from inside the skull to structures of the inner ear and face. It also contains the vestibular ganglion.

Additional images

See also

Related Research Articles

<span class="mw-page-title-main">Facial nerve</span> Cranial nerve VII, for the face and tasting

The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue. The nerve typically travels from the pons through the facial canal in the temporal bone and exits the skull at the stylomastoid foramen. It arises from the brainstem from an area posterior to the cranial nerve VI and anterior to cranial nerve VIII.

Articles related to anatomy include:

<span class="mw-page-title-main">Vestibulocochlear nerve</span> Cranial nerve VIII, for hearing and balance

The vestibulocochlear nerve or auditory vestibular nerve, also known as the eighth cranial nerve, cranial nerve VIII, or simply CN VIII, is a cranial nerve that transmits sound and equilibrium (balance) information from the inner ear to the brain. Through olivocochlear fibers, it also transmits motor and modulatory information from the superior olivary complex in the brainstem to the cochlea.

<span class="mw-page-title-main">Temporal bone</span> Bone of the neurocranium

The temporal bones are situated at the sides and base of the skull, and lateral to the temporal lobes of the cerebral cortex.

<span class="mw-page-title-main">Saccule</span> Bed of sensory cells in the inner ear

The saccule is a bed of sensory cells in the inner ear. It translates head movements into neural impulses for the brain to interpret. The saccule detects linear accelerations and head tilts in the vertical plane. When the head moves vertically, the sensory cells of the saccule are disturbed and the neurons connected to them begin transmitting impulses to the brain. These impulses travel along the vestibular portion of the eighth cranial nerve to the vestibular nuclei in the brainstem.

<span class="mw-page-title-main">Posterior cranial fossa</span> Area of the cranium containing the brainstem and cerebellum

The posterior cranial fossa is the part of the cranial cavity located between the foramen magnum, and tentorium cerebelli. It is formed by the sphenoid bones, temporal bones, and occipital bone. It lodges the cerebellum, and parts of the brainstem.

<span class="mw-page-title-main">Tympanic cavity</span> Small cavity surrounding the bones of the middle ear

The tympanic cavity is a small cavity surrounding the bones of the middle ear. Within it sit the ossicles, three small bones that transmit vibrations used in the detection of sound.

<span class="mw-page-title-main">Jugular foramen</span> Opening in the base of the skull allowing many structures to pass

A jugular foramen is one of the two large foramina (openings) in the base of the skull, located behind the carotid canal. It is formed by the temporal bone and the occipital bone. It allows many structures to pass, including the inferior petrosal sinus, three cranial nerves, the sigmoid sinus, and meningeal arteries.

<span class="mw-page-title-main">Greater wing of sphenoid bone</span> Large part of the skull front behind the eye socket

The greater wing of the sphenoid bone, or alisphenoid, is a bony process of the sphenoid bone, positioned in the skull behind each eye. There is one on each side, extending from the side of the body of the sphenoid and curving upward, laterally, and backward.

<span class="mw-page-title-main">Labyrinthine artery</span> Artery of the internal ear

The labyrinthine artery is a branch of either the anterior inferior cerebellar artery or the basilar artery. It accompanies the vestibulocochlear nerve through the internal acoustic meatus. It supplies blood to the internal ear.

<span class="mw-page-title-main">Carotid canal</span> Hole in the temporal bone in the skull for the internal carotid artery to enter the skull

The carotid canal is a passage in the petrous part of the temporal bone of the skull through which the internal carotid artery and its internal carotid (nervous) plexus pass from the neck into the cranial cavity.

<span class="mw-page-title-main">Squamous part of temporal bone</span> Front and upper part of the sides of the skull base

The squamous part of temporal bone, or temporal squama, forms the front and upper part of the temporal bone, and is scale-like, thin, and translucent.

<span class="mw-page-title-main">Petrous part of the temporal bone</span> Feature at the base of the human skull

The petrous part of the temporal bone is pyramid-shaped and is wedged in at the base of the skull between the sphenoid and occipital bones. Directed medially, forward, and a little upward, it presents a base, an apex, three surfaces, and three angles, and houses in its interior, the components of the inner ear. The petrous portion is among the most basal elements of the skull and forms part of the endocranium. Petrous comes from the Latin word petrosus, meaning "stone-like, hard". It is one of the densest bones in the body. In other mammals, it is a separate bone, the petrosal bone.

<span class="mw-page-title-main">Facial canal</span> Hole in the temporal bone of the skull carrying the facial nerve

The facial canal is a Z-shaped canal in the temporal bone of the skull. It extends between the internal acoustic meatus and stylomastoid foramen. It transmits the facial nerve.

<span class="mw-page-title-main">Middle cranial fossa</span>

The middle cranial fossa is formed by the sphenoid bones, and the temporal bones. It lodges the temporal lobes, and the pituitary gland. It is deeper than the anterior cranial fossa, is narrow medially and widens laterally to the sides of the skull. It is separated from the posterior cranial fossa by the clivus and the petrous crest.

<span class="mw-page-title-main">Subarcuate fossa</span> Depression in the temporal bone in the skull of mammals

The subarcuate fossa is a shallow depression upon the internal surface of the petrous part of the temporal bone forming the wall of the posterior cranial fossa. The fossa accommodates the flocculus of the cerebellum. It is situated lateral/posterior to the internal auditory meatus.

<span class="mw-page-title-main">Vestibule of the ear</span> Central part of the bony labyrinth

The vestibule is the central part of the bony labyrinth in the inner ear, and is situated medial to the eardrum, behind the cochlea, and in front of the three semicircular canals.

<span class="mw-page-title-main">Base of skull</span> Inferior area of the skull, composed of the endocranium and lower parts of the skull roof

The base of skull, also known as the cranial base or the cranial floor, is the most inferior area of the skull. It is composed of the endocranium and the lower parts of the calvaria.

<span class="mw-page-title-main">Outline of human anatomy</span> Overview of and topical guide to human anatomy

The following outline is provided as an overview of and topical guide to human anatomy:

References

PD-icon.svgThis article incorporates text in the public domain from page 143 of the 20th edition of Gray's Anatomy (1918)

  1. Kozerska, M; Skrzat, J (2015). "Anatomy of the fundus of the internal acoustic meatus — micro-computed tomography study". Folia Morphol. 74, 3 (3): 352–358. doi: 10.5603/FM.2015.0053 . PMID   26339817.
  2. Brennan, Peter Prof.; Standring, Susan; Wiseman, Sam (5 November 2019). Gray's Surgical Anatomy E-Book. Elsevier Health Sciences. p. 155. ISBN   9780702073885 . Retrieved 20 March 2022.