Gross Anatomy

Middle Ear

Anatomy Tables for Today's Topic

Bones of the Ear
Muscles of the Ear
Nerves of the Ear
Arteries of the Ear

Bones of the Ear

Bone/Cartilage Structure Description Notes
temporal bone forming the lateral side of the skull temporal refers the passage of time, which is marked by the appearance of gray hair on the side of the head
petrous part the hard part of the temporal bone located in the floor of the cranial cavity it contains the tympanic cavity (middle ear) and the bony labyrinth of the inner ear
internal acoustic meatus the opening on the posteromedial surface of the petrous part of the temporal bone it transmits the facial n., the vestibulocochlear n., and the labyrinthine a.
external acoustic meatus the opening in the lateral surface of the temporal bone it extends medially from the surface to the tympanic membrane; it allows sound to reach the tympanic membrane; the medial 1/3 of the external acoustic meatus is bony and the lateral 2/3 is formed by cartilage
facial canal a canal which courses through the petrous part of the temporal bone it transmits the facial n. from the internal acoustic meatus to the stylomastoid foramen
carotid canal a canal which courses through the petrous part of the temporal bone it transmits the internal carotid a. and the internal carotid plexus of nerves into the cranial cavity
mastoid process the process located posteroinferior to the external acoustic meatus it projects inferiorly from the junction of the petrous and squamous parts of the temporal bone; it contains the mastoid air cells that open into tympanic cavity through the mastoid antrum
tegmen tympani thin plate of bone forming the roof of the tympanic cavity located on the floor of the middle cranial fossa
jugular fossa a depression on the posterior surface of the petrous part of the temporal bone it forms the anterior margin of the jugular foramen; the occipital bone forms the posterior margin of the jugular foramen
styloid process the spike of bone that projects inferiorly from the petrous part of the temporal bone it is the attachment site for the stylohyoid, styloglossus and stylopharyngeus mm. and the stylomandibular and stylohyoid ligaments
tympanic part the part of the temporal bone consisting of the external acoustic meatus and the tympanic ring the medial 1/3 of the external acoustic meatus is bony and the lateral 2/3 is formed by cartilage
tympanic ring the rim of bone surrounding the medial end of the external acoustic meatus it is the attachment site of the tympanic membrane
ossicles a chain of three bones in the tympanic cavity (middle ear) connecting the tympanic membrane to the oval window; arranged from lateral to medial: malleus, incus, stapes the ossicles are joined by synovial articulations that may become arthritic in old age, resulting in conductive deafness
incus the middle ossicle of the middle ear articulates with the head of the malleus and the head of the stapes; incus means "anvil"
malleus the lateral ossicle of the middle ear the manubrium is attached by its handle to the inner surface of the tympanic membrane at the umbo; its head articulates with the incus; malleus means "hammer"
stapes the medial ossicle of the middle ear it articulates with the long process of the incus and its base fills the fenestra vestibuli (oval window); stapes means "stirrup"

Muscles of the Ear

Muscle Origin Insertion Action Innervation Artery Notes
stapedius walls of the pyramidal eminence neck of the stapes dampens vibration of the stapes facial nerve (VII) anterior tympanic a. entirely enclosed in bone, except for its tendon; a derivative of the second pharyngeal arch
tensor tympani cartilagenous auditory tube and the greater wing of the sphenoid bone which lies adjacent to it manubrium of the malleus dampens vibrations of the tympanic membrane medial pterygoid branch of the mandibular division of the trigeminal nerve (V) superior tympanic branch of the middle meningeal a. V3 innervates both tensor muscles of the head (tympani and veli palatini) which are derivatives of the first pharyngeal arch

Nerves of the Ear

Nerve Source Branches Motor Sensory Notes
facial n. pons and medulla: nucleus solitarius of medulla via nervus intermedius (SVA sensory root) from geniculate ganglion; superior salivatory nucleus (GVE preganglionic parasympathetic) of pons via nervus intermedius; facial motor nucleus of pons via motor root greater petrosal n. (preganglionic parasympathetic to pterygopalatine ganglion, postganglionic parasympathetic travels with brs. of maxillary division of V), chorda tympani (SVA taste from anterior 2/3 of the tongue; preganglionic parasympathetic to the submandibular ganglion, postganglionic parasympathetic to the submandibular and sublingual glands), n. to stapedius, posterior auricular n., intraparotid plexus with temporal, zygomatic, buccal, marginal mandibular & cervical brs. stapedius m., stylohyoid m., posterior belly of digastric m., muscles of facial expression; secretomotor to lacrimal, submandibular, sublingual, and mucous glands of the nasal and oral cavities taste (SVA) from the anterior 2/3 of the tongue; part of the skin of the external auditory meatus also known as: CN VII, 7th cranial nerve; exits the posterior cranial fossa by passing into the internal acoustic meatus, goes through the facial canal; motor to muscles of facial expression exits the skull at the stylomastoid foramen
ganglion, geniculate facial n. (VII) (chorda tympani branch) nervus intermedius (SVA sensory root of facial n.) none taste (SVA) from the anterior 2/3 of the tongue a sensory ganglion equivalent in histological structure and function to a dorsal root ganglion; some taste from the palate travels through the greater petrosal n. to the geniculate ganglion; located in the facial canal within the petrous portion of the temporal bone
greater petrosal n. facial (VII) no named branches secretomotor (preganglionic parasympathetic) to: lacrimal gland, mucous glands of the lower nasal cavity, maxillary sinus and palate none greater petrosal n. joins the deep petrosal n. to form the n. of the pterygoid canal; the greater petrosal n. contains: preganglionic parasympathetic axons bound for the pterygopalatine ganglion where they will synapse; it passes through the hiatus of canal of greater petrosal n. in the petrous part of the temporal bone
chorda tympani facial (VII) no named branches secretomotor to the submandibular and sublingual glands (it carries preganglionic parasympathetic axons to the submandibular ganglion) taste to the anterior 2/3 of the tongue chorda tympani joins the lingual nerve in the infratemporal fossa and continues with it to the tongue
cochlear n. vestibulocochlear n. no named branches none hearing (SSA) exits the posterior cranial fossa by passing into the internal acoustic meatus
vestibular n. pons and medulla no named branches none balance/proprioception (SSA) vestibular n. is part of the vestibulocochlear n.
vestibulocochlear n. pons & medulla: vestibular nuclei from the vestibular ganglion of the semicircular ducts; cochlear nuclei in the inferior cerebellar peduncle divides within the temporal bone into vestibular and cochlear parts none vestibular: balance/proprioception (SSA); cochlear: hearing (SSA) also known as: CN VIII, 8th cranial nerve; auditory nerve; passes into the internal auditory meatus
glossopharyngeal n. medulla: spinal trigeminal nucleus from the superior ganglion (GVA); nucleus solitarius from the inferior ganglion (SVA); nucleus ambiguus (GVA); inferior salivatory nucleus (GVE - preganglionic parasympathetic) tympanic nerve to the tympanic plexus and lesser petrosal n., carotid sinus n., stylopharyngeus brs., pharyngeal brs. GSE: stylopharyngeus; GVE: secretomotor to the parotid gland (preganglionic parasympathetic via the tympanic n. to the lesser petrosal n. to the otic ganglion; postganglionic parasympathetic via the auriculotemporal n.) GVA: carotid body, carotid sinus, pharynx, middle ear; GSA: skin of the external ear; SVA: taste from the posterior 1/3 of the tongue also known as: CN IX, 9th cranial nerve; the glossopharyngeal n. exits the posterior cranial fossa by passing through the jugular foramen;it may penetrate the stylopharyngeus m.
tympanic n. glossopharyngeal n. tympanic plexus, which gives rise to the lesser petrosal n. secretomotor (preganglionic parasympathetic axons which will synapse in the otic ganglion) to the parotid gland mucous membrane lining the middle ear cavity tympanic n. passes from the inferior ganglion of CN IX through the tympanic canaliculus to reach the middle ear
ganglion, spiral fibers of the cochlear hair cells cochlear n. portion of the vestibulocochlear n. (VIII) none hearing (SSA) a sensory ganglion of the cochlear part of CN VIII

Arteries of the Ear

Artery Source Branches Supply to Notes
labyrinthine anterior inferior cerebellar a. (or basilar a.) no named branches internal ear labyrinthine a. accompanies cranial nerves VII and VIII through the internal acoustic meatus

Other Tables of Interest:

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Some of the material presented in these tables is contained in the book:
MedCharts Anatomy by Thomas R. Gest and Jaye Schlesinger
Published by ILOC, Inc., New York. Copyright 1995.

Content of these tables has been edited for use in this course by Patrick W. Tank, Ph.D.
Copyright 2007, Department of Neurobiology and Developmental Sciences, University of Arkansas for Medical Sciences.

Unauthorized use is prohibited.