Clinical anatomy & physiology of the ear

Anatomy of ear

• Located On both sides of cranial bone. Close with parietal bone, sphenoid bone

and occipital bone

• Composition: squamaous, tympanic, mastoid and petrous parts + styloid process

Temporal bone

Temporal bone and its abutment1.Occipitomastoid suture 2.Squamosomastoid suture3.Occipital bone4.Parietomastoid suture5.Squamous suture6.Parietal bone 7.Temporal bone8. Sphenosquamosal suture9. Frontal bone10.Spheoid bone11.Zygomatic bone12.Mandible 13.External acoustic meatus

External surface of left tymporal bone in adult1.External acoustic meatus 2.Suprameatal trinangle3.Squamous part 4.Mastoidale5.Tympanomastoid fissure6.Zygomatic process 7.Mandibular fossa8.Tymporal line 9.Tympanosquamous fissure 10. Styloid process

Internal surface of left tymporal bone in adult11.Sulcus for middle meningeal artery12.Petrous bone 13. Inner acoustic meatus 14.Sigmoid sulcus15.Sulcus for superior petrosal sinus16.Sulcus for inferior petrosal sinus17. Petrous apex 18 = Arcuate eminence19 = Inner orifice of internal carotid canal

9.Notch of rivinus 10. Suprameatal spine11.Suprameatal triangle12.Temporal linef 13.Parietal notch 14.External acoustic foramen15.Mastoid part16.Occipital margin17.Sutura mastoideosquamalis18.Mastoid foramen19.Tympanomastoid fissure

External surface of tymporal bone

1.Margo parietalis2.Squamous part3.Temoral surface 4.Margo sphenoidalis 5.Processus retroarticularis6.Zygomatic process7.Articular tubercle8.Mandibular fossa

20.Mastoid notch 21.Mastoid22.Petrotympanic fissure 23.Tympanic part24.Styloid process

Internal surface of tymporal bone

5.Posterior branch sulcus of middle meningeal artery6.Arcuate eminence 7.Groove for superior perosal sinus8.Internal auditory foramen 9.Styloid process

1.Sutura petrosquamosa 2.Sigmoid sulcus 3.Mastoid foramen 4.Orifice of vestibular aqueduct

Inferior surface of tymporal bone

1.Caroticotympanic canals2.Carotid canal 3.Tympanic canaliculus for jacobson nerve4.Sulcus of mastoid canaliculus 5.External aperture of aqueduct of cochlea6.Mastoid canaliculus for arnold nerve 7.Jugular fossa

8.Zygomatic process9.Articular tubercle 10.Articular fossa of mandible 11.Tympanosquamous fissure12.Tympanic part 13.Styloid process 14.External acoustic foramen15.Styloimastoid foramen 16.Mastoid 17.Mastoid notch18.Sulcus for occipital artery 19.Mastoid part

Anatomic relationship of fundus of internal acoustic meatus

3.Area of facial nerve4.Superior vestibular area5.Vertical crest6.Inferior vestibular area7.Haplopore8.Central canal of cochlea

1.Transverse crest2.Cochlear area（ Tractus spiralis foraminosus ）

External ear

Anatomy of external ear

• Pinna of ear anterior notch of ear • External acoustic meatus– 2.5-3.5cm– Lateral 1/3 : cartilage; medial 2/3: bone– 2 stenosis ： Juncture between bone and cartilage Isthmus of external acoustic meatus

Anatomy of external ear

1.Triangular fossa2.Cymba of auricular concha 3.Cavity of auricular concha4.Auricular concha5.Anterior incisure of ear 6.Tragus7.Intertragic notch8.Ear lobe

9.Helix10.Superior crura of antihelix 11.Inferior crura of antihelix12.Auricular tubercle 13.Scaphoid fossa 14.Antihelix 15.Crus of helix 16.External acoustic meatus19.Antitragus

Middle ear

Anatomy of middle ear

• Tympanic cavity• Eustachian tube• Tympanic sinus• Mastoid

Anatomy of middle ear

• Delimitation according to membrane tensa

Attic

Mesotympanum

Hypotympanum

Internal surface of tympanic lateral wall

1.Incudomallear articulation

2.Superior ligament of malleus

3.Head of malleus 4.Tympanic attic5.Processus anterior

mallei 6.Anterior fold of

tympanic membrane 7.Anterior fossa of

tympanic membrane 8.Cord of tympanum9.Eustachian tube

12.Body of incus13.Short crus of incus14.Tympanic antrum 15.Posterior ligament

of incus in incudal fossa

16. Posterior fold of tympanic membrane

17.Long crus of incus 18. Posterior fossa of

tympanic membrane

19.Lenticular process of incus

20.Tympanichordal pathway 10.Limbus membranae tympani

11.Pars tensa21.Tensor tympani muscle 22.Handle of malleus

Tympanic membrane

• Tympanic membrane(TM)

semi-transparent film,

9*8*0.1mm3

flaccid part ， tensa part

3 layered structure:

Epithelial lamina

Fibrous lamina

Mucous lamina

TM1.Flaccid part 2.Short process of

malleus3.Handle of malleus4.Tensa part 5.Light cone

Internal wall of tympanum• Internal wall of middle ear

=lateral wall of inner ear

Center - Promontorium tympani

Posterosuperior –vestibular window(oval window)-vestibule

Posteroinferior – cochlear window(round window)-Scala tympani

Superior of vestibular window – horizontal part of fallopian

aqueduct

Posterosuperior of fallopian aqueduct – prominence of lateral

semicircular canal

Anterior of vestibular window – cochleariform process

Internal wall of tympanum

Glomus jugulare

Carotid artery

Fossula of round window

Tympanic membrane

Chorda tympani nerve

Incus

MalleusTensor tympani muscle Ostium tympanicum

tubae auditivae

Canal for tensor tympani muscle

Promontorium tympani

Tymporal lobe

Cochleariform process

Orifice of chorda tympani nerveFicial nerve

Pyramidal eminenceProminence of lateral semicircular canal

Prominence of facial canal Stapedial footplate

Aditus ad antrum

Anterior wall of tympanum

• Anterior wall of middle ear = carotid wall

separated inferiorly by carotid

2 orifices in superior part:

orifice of canalis tensor tympani (superior)

orifice of semicanalis eustachii (inferior)

Anterior wall of tympanum

1.Tympanic attic 2.Stapes 3.Tegmen tympani 4.Tendon of tensor tympani muscle5.Cochleariform process6. Greater superficial

petrosal nerve7.Lesser petrosal nerve 8.Bony septum of eustachian canal 9.Tensor tympani muscle10.Eustachian tube11.Carotid wall of

tympanum12.Labyrinthine wall of

tympanum

13.Head of malleus 14.Superior ligament

of malleus 15.Neck of malleus 16.Anterior process

and ligament of malleus

17. Lateral process of malleus(short process of malleus)

18.Handle of malleus19.Umbo of tympanic

membrane20.Limbus membrane

tympani

21.Fibrocartilaginous ring 22.Tympanic sulcus

Posterior wall of tympanum• Posterior wall - mastoid wall

Superior orifice –aditus ad antrum

Incudal fossa – posterior junction of horizontal and

vertical segment of fallopian aqueduct

Height of vestibular window – pyramidal eminence

facial recess – posterior tympanic approach

Posterior wall of tympanum

1.Stapes 2.Incus 3.Chorda tympani nerve 4.Facial recess 5.Chorda tympanic crest 6. Chorda tympanic eminence 7.Pyramidal eminence 8.Lateral sinus tympani9.Styloid process eminence

10.Malleus 11.Sinus tympani 12.Fossula of cochlear window

Superior and inferior wall of tympanum

• Superior wall - tegmen tympani

separated with temporal lobe in middle cranial fossa

Petrosquamous suture in infant is not close yet

-infection of middle ear invade into cranium

• Posterior wall - Jugular wall

separated with glomus jugulare

if deletion of posterior wall – blue drum

Content of tympanum

• Auricular bone (the smallest bone): Malleus, incus, stapes – ossicular chain

• Ligament of auricular bone

• Tympanic muscle: tensor tympani muscle, stapedius muscle• Chorda tympani nerve

1.Superior ligament of malleus 2.Anterior ligament of malleus3.Tensor tympani muscle

4.Superior ligament of incus5.Posterior ligament of incus6.Stapedius muscle

Eustachian tube• Passway between tympanum and nasopharynx.

• Lateral 1/3: bony part, medial 2/3 ： cartilaginous par

• Junction between bony and cartilaginous: isthmus

• Regulate tympanic pressure

1.Incus2.Tympanic membrane 3.Mandibular fossa4.Styloid process5.Carotid artery

6.Tensor tympani muscle7.Pharyngeal opening of auditory tube

Tympanic antrum1.Tympanic antrum2.Tygmen tympani 3.Lateral semicircular duct4.Fallpian aqueduct5.Vestibular window6.Canal for tensor tympani muscle7.Bony septum of eustachian canal8.Hiatus canalis facialis9.Carotid canal10.Bony part of auditory tube11.Promontorium tympani12.Pyramidal eminence13.Cochlear window14.Tympanic sulcus15.Stylomastoid foramen16.Mastoid air cell

Mastoid

• Mastoid: intratemporal cells• Typing: pneumatic type, dipoetic type, sclerotic type, mixed type• Distribution: mastoidale group, perisigmoid group,

antrodural group, perilabyrinthine group,

epidural group, zygomatic group,

perifacial group.

Anatomy of inner ear

• labyrinth ， including receptor of auditory and

equilibratory sensation• Contain ： bony and membrane labyrinth• Perilymph ： between bony and membrane labyrinth, K↓Na↑• Endolymph: in endolymphatic labyrinth, K↑Na↓

Anterolateral view of bony labyrinth

• Bony labyrinth: vestibule, semicircular canals,cochlea

1.Anterior semicircular canal 2.Common crus 3.Lateral bony ampulla 4.Crura ampullaria 5.Crus simplex 6.Lateral semicircular duct 7.Vestibular window 8.Posterior semicircular canal 9.Posterior bony ampulla

10.Anterior bony ampulla

11.Utricle 12.Sacculus13.Vestibule 14.Cupula of

cochlea15.Cochlear

middle cycle16.Cochlear top

cycle 17.Cochlear basic

cycle18.Vestibular crest19.Cochlear

window

Internal view of bony labyrinth

1.Anterior semicircular canal2.Common crus 3.Lateral semicircular canal4.Posterior semicircular canal5.Pars ampullaris6.Orifice of vestibular aqueduct 7.Cochlear recess

8.Orifice of common crus9.Utricular recess 10.Vestibular crest 11.Spherical recess 12.Cochlea 13.Scala tympani 14.Bony spiral lamina 15.Scala vestibuli 16.Orifice of

cochlear aqueduct

17. Cochlear window

Vestibule

• Located between cochlea and semicircular canals

• Spherical recess, utricular recess

• Lateral wall: vestibular window, stapedial footplate

Bony semicircular canals

• 3 curved bony canals, perpendicularly, lateral,superior, posterior semicircular canals.

• Common crus: superior and posterior canals• Position of semicircular canals

Membranous labyrinth• Composition: Utricle, sacculus, membranous

semicircular canals and membranous cochlear canal

1.Anterior semicircular canal2.Common crus 3.Semicircular canal isthmus 4.Posterior semicircular canal5.Lateral semicircular canal6.Endolymphatic sac

7.Pars ampullaris8.Utricle 9.Utricle duct10.Saccule 11.Saccule duct12.Union duct13.Vestibular

cecum14.Semicircular

canal sinus15.Pars

ampullaris

Membranous labyrinth

• Utricle

• Sacculus

• Membranous semicircular canals

•Membranous cochlear canal: between bony spiral lamina and lateral wall of bony cochlear duct

18.Basilar membrane 19.Corti’s tunnel 20.inner and outer pillar cell 21. Scala tympani 22.tympanic pic 23.inner spiral sulcus

1.Spiral limbus 2.Vestibular lip 3.Internal beam of spiral ganglion4.Spiral ganglion 5.Scala vestibuli 6.Vestibular membrane

7.Inner hair cells 8.Outer hair cell 9.Tectorial membrane 10.Hensen cell11.Claudius cell

12.Vestibular membrane crest

13.Stria vascularis 14.Spiral prominence 15.External spiral

sulcus 16.Basilar membrane 17. Spiral ligament of

cochlea

Membranous labyrinth

•Basilar membrane

11.Claudius cell 12. Deiters cell 13.outer pillar cell 14.Corti’s tunnel15.Basilar membrane 16.spiral vessel 17.inner pillar cell 18.tympanic

lip 19.nerve fibers 20.arcuate zone 21.Pectinate zone

1.Spiral limbus 2.Vestibular lip 3.Tectorial membrane4. Outer hair cell 5.Outer tunnel 6.Henson cell7.Inner spiral sulcus 8.Marginal cell 9.Inner hair cell10.NueI interspace

Membranous labyrinth

Model of acoustic transduction

1.Medial longitudinal bundle 2.Superior nucleus 3.Lateral nucleus 4.Medial nucleus5.Inferior nucleus 6.Vestibulospinal tract 7.Vestibular ganglion

Model of acoustic transduction

1.Auditory cortex 2.Dorsal acoustic striae3.Middle acoustic striae 4.Gastral acoustic striae5.Reticular formation 6.Medial geniculate body7.Inferior colliculus 8.Nucleus dorsalis9.Lateral lemniscus 10.Ventralis anterior11.Superior olivary

nuclear complex 12.Cochlear dorsal

nucleus13.Cochlear gastral

nucleus

Central passway of vestibular nerve

1.Auditory cortex 2.Brachium quadrigeminum inferius 3.Cochlea 4.Medial geniculate nucleus 5.Nucleus of inferior colliculus6.Nucleus of lateral lemniscus 7.Superior olivary nuclear

complex8.Cochlear nucleus

Physiology of ear

• Auditory perception

• Equilibratory sensation

Sound afferent passway

• Air conduction ： sound wave → pinna of ear→ external acoustic meatus

→ auditory ossicles → vestibular window → perilymph,

endolymph → Spiral organ of Corti → acoustic nerve →

different levels of nucleus → acoustic center

Sound afferent passway

• Bone conduction

translatory mode of bone conduction

compressonal mode of bone conduction

Physiology of external ear

• Sound collection

• Distinguish direction

• Sympathetic vibration

• Protection

• Sound pressure amplification

Physiology of middle ear

• Sound transformation and gain of middle ear

• Sound transmission and transformation structure:

tympanic membrane and ossicular chain

Physiology of middle ear

Effective vibrative aera: 55 mm2 , 2/3 of anatomic area.

Stapedial footplate area: 3.2 mm2 , 1/17 of effective

vibrative area

•Pressure = Force/area

•Area of tympanic membrane ~17 > area stapes

•Gain of area ratio ~24 dB

Function Middle ear: amplification from area ratio

•Energy loss at air-fluid interface-99.9% loss (-30 dB)

•Malleus longer than incus-amplify pressure ~1.7X (+2 dB)

Function of Middle ear—pressure amplification-ossicles

Physiology of tympanic muscle

• Stapedius muscle

• Tensor tympani muscle

Physiology of eustachian tube

• Maintains pressure balance between middle ear and outside

• Drainage • Prevent retrograde infection• Prevent strong sound

Auditory physiology

• Sound transduction• Sound perception

Basilar membrane displacement for a 1 kHz tone

Basilar membrane displacement for a 250 Hz tone

Basilar membrane displacement for a 4 kHz tone

•Mass & stiffness gradient gives rise to a so-called “traveling wave”Mass & stiffness gradient gives rise to a so-called “traveling wave”

•Characteristic frequency—frequency which produces the largest amplitude of Characteristic frequency—frequency which produces the largest amplitude of responseresponse

•Apex-maximum response to low frequenciesApex-maximum response to low frequencies

•Base maximum response to high frequenciesBase maximum response to high frequencies

Mass-increases from base (stapes) to apex

Stiffness-increases from apex to base

1

23

4

Envelope of traveling wave

Characteristic frequency

Cochlear mechanical response due mass and stiffness gradient

Stereocilia on OHCs attached to tectorial membrane

Stereocilia on IHCs free standing

Motion of basilar membrane towards scala vestibuli deflects stereocilia in excitatory direction

Tectorial membrane deflects OHC stereocilia

Viscous fluid drag of fluid deflects IHC stereocilia

•Model: OHC contraction cause organ of Corti to distort as shown here •Cell motility feeds back enhancing basilar membrane motion thereby increasing traveling wave amplitude and making the “cochlea active”

Corti’s organ responds OHC’s electromotion

OHC

Physiology of quilibrium

•Equilibrium is the state of balance of the body.

•An erect standing human has a highly unstable equilibrium.

•Through a variety of sensory inputs (vestibule,visual and so forth)

and postural reflexes (proprioception), the body is maintained in its

erect posture.

•Vestibule: Recognize linear acceleration by otolithic macula (utricle

+ saccule)

•Semicircular canal: receptor of positive and negateive angular

acceleration

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