Ear Anatomy and Physiology Guide by Dr. Tarun Kumar Dwibedi

Dr. Tarun Kumar Dwibedi / 9438790500 / dr.tarun52@gmail.com / SJG AMC & H, KOPPAL
THE EAR
DR.TARUN KUMAR DWIBEDI
PG scholar, DEPT. Shalakya Tantra
SJG AMC & H, KOPPAL.

RELATION OF EAR
• SUPERIORLY – MIDLE CRANEAL FOSSA
• INFERIORLY – PAROTID GLAND
• ANTERIORLY –TEMPOROMANDIBULAR JUNCTION
• POSTERIORLY – MASTOID AIR CELLS

EAR STRUCTURES
1. EXTERNAL EAR
2. MIDDLE EAR
3. INTERNAL EAR
EXTERNAL EAR
PINNA
EAC
TYMPANIC MEMBRANE
MIDDLE EAR
MIDDLE EAR CLEFT
OSSICLES – MIS
WALLS – 6
INTERNAL EAR
BONY LABIRYNTH
MEMBRANEOUS LABIRYNTH
• ORGAN OF CORTI – FUNCTIONAL UNIT OF HEARING
• MACULA

EXTERNAL EAR
• PINNA
• EXTERNAL AUDITORY MEATUS
• TYMPANIC MEMBRANE
PINNA
• SINGLE YELLOW ELASTIC CARTELAGENEOUS FRAMEWARK
• THE SPACE BETWEEN CRUS OF HELIX AND THE TRAGUS DEVOID OF THE ELASTIC
CARTELAGENEOUS FIBER – INSISURA TERMINALIS
• MANY ELEVATION AND DEPRESSION
• HELIX , ANTI HELIX, TRAGUS. ANTI TRAGUS, SCAPHOID FOSSSA , TRIANGULAR FOSSA
FROM CONCHA OPENING OF EAC
• THE LOWER HANGING PART DEVOID OF YELLOW ELASTIC FIBER KNOWN AS
THE LOBULE.

THE PINNA

EXTERNAL AUDITORY MEATUS
• 24 mm
• 2 PART
• OUTER CARTELAGENEOUS 8 mm
• INNER BONY PART 16 mm
• NOT STRAIGHT - UPWARD  BACK WARD MEDIALLY
• HENCE TO EXAMINE EAC WE NEED TO STRETCH THE EAR PINNA UPWARD AND BACK WARD.
• SKIN OF ANTERIOR PART OF PINNA TIGHTLY ADHER TO THE FRAME WORK THAN THE POSTERIOR SKIN OF THE PINNA.
OUTER CARTELAGENOUS PART
SKIN CONTAINS CERUMINOUS GLAND & PILO-SEBASEOUS GLAND -- WAX
IT HAS HAIR FOLLICLES HENCE PRONE TO FURUNCULOSIS
INNER BONY PART
NO GLANDS AND FOLLICLES
6 mm FROM TM THRERE IS A NARROWING CALLED AS THE ISTHMUS
SKIN OF THIS PART CONTINUES AS THE OUTER SKIN OF TM.

TYMPANIC MEMBRANE
• oblique  postero-superior part is more lateral than the antero- inferior part
• vertical diameter – 9-10 mm
• horizontal diameter – 8-9mm
• thickness - 0.1 mm
• has 2 part – pars tensa & pars flaccida
• cone of light seen at the antero inferior part of tm.
• LAYERS –
outer- skin of bony part
middle- fibrous -3 layered – radial, vertical and parabolic
lateral process of malleus is connected to fibrous layer
inner – mucosal layer of middle ear.
PARS TENSA
Most part of tm .
Periphery is thicker than
the central part and
forms a fibro elastic ring –
annulus tympanicus fixed
in to the tympanic fossa.
Central part posteriorly
stretched by the handle of
malleus .
This part is the umbo.
The imaginary line drawn
From umbo divides the tm
in to anterior and poste.
quadrant.
PARS FLACCIDA
Extends from the lateral
process of malleus and
between the ant. And post.
f malleal Fold.
Slightly pinkish

MIDDLE EAR
MIDDLE EAR CLEFT
• Eustachian tube + aditus + antrum +Mastoid air cell

EAR OSSICLES – MIS
• Malleus – 8 mm
• Head , Neck , Handle , ant. & lateral process.
• Handle attached to the fibrous layer of TM.
• Head with the body of incus
• Tensor tympani attached to the neck

STAPEDIUS

INCUS
Body , short process, long process
Body articulate with head of malleus
Long process articulates with head of stapes

• STAPES - 5 mm
• Smallest bone of body
• Head, NECK , ante. & Post. Crus
• Foot plate – connected to the oval window
• Head articulate with long process of incus
• Stapedius , the smallest muscle attached to
the neck of stapes

• WALLS OF MIDDLE EAR – 6
1. ROOF
2. FLOOR
3. ANTERIOR WALL
4. POSTERIOR WALL
5. LATERAL WALL
6. MEDIAL WALL

ROOF
Formed by tegmen tympani
Separates middle cranial fossa
FLOOR
Separates from jugular bulb
ANTERIOR WALL
Separates from int. Carotid artery
Has 2 opening 1 & 2
1. Above for tensor tympani
2. Below for Eustachian tube

POSTERIOR WALL
• Triangular elevation – pyramid – origin of stapedius
• Above the pyramid the opening of the mastoid
i.e.. Aditus.
• Lateral to the pyramid , the facial nerve.
• There is a depression known as the
Facial recess just lateral to the pyramid.

• LATERAL WALL
Has tympanic membrane ,the window

MEDIAL WALL
• Has 2 Opening / Window (No. 3 & 5)
• No.3 Oval Window For Footplate Of Stapes
• No.4 Round Window For Secondary Tm
• Ant. To Oval Window A Hook Like Structure –
Processus Cochleariformis
• Above The Oval Window – Canal For Cn.Vii
• Medial To The Pyramid A Depression -
Sinus Tympani

INTERNAL EAR
BONY LABIRYNTH
MEMBRANEOUS
LABIRYNTH
BONY LABIRYNTH
COCHLEA
• 2.5- 2.75 turn around a central axis –
modiolus
• Modiolus has spiral lamina on which
the basilar membrane rests.
• Has 3 compartment scala tympani,
scala vestibule (has perilymph),Scala
media – (has endolymph)
• At apex S. V & S.T connects with
helicotrema
VESTIBULE
• Has 2 Opening i.e.. Oval & Round
Window
• Inside To The Medial Wall A Spherical
Recess Lodging Saccule, Below It Has
Elliptical Recess Lodging Utricle.
• Below The Elliptical Recess The
Opening
• Of Aqueduct Of Vestibule.
SEMICIRCULAR CANAL
• 3 scc. Perpendicular to each.
• Superior- posterior- lateral.
• Each crus has an ampulated & an
unampulated end
• Has 5 opening as the unamulated
crus of post. & superior SCC are
fused known as crus commune.
• Those are open to the vestibule.

MEMBRANEOUSLABIRYNT
H
COCHLEAR DUCT
SACCULE & COCHLEA
SEMICIRCULAR DUCT
COCHLEAR DUCT
• Filled with endo lymph
• Blind – no opening
• Has 3 wall
1. Basillar memb. Separates
S.T. from S.M. & Lodges organ of corti
2. Stria vascularis - secretes endo lymph
3. Ressiners membrane – separates S.V
from S. M
SACCULE & UTRICLE
• Saccule – connects with utricle by
utriculo saccular duct
• Macula is the sensitive part
• Has vertical sensitive epithelium.
• Joins with cochlea by ductus reuniens.
• Utricle- has 5 opening for scc.
• Has macula- horizontal sensitive
epithelium on floor
• Both are responsible for balance in linear
and accelerative movement.
SCC DUCT
• 3 in no.
• Present In side the SCC.
• The ampulated end has sensitive neuro
epithelium for balance in rotational
movement – crista ampularies.
The 2 duct 1 from each utricle and saccule forms the endolymphatic duct, Which at
end dilated to form the endolymphatic SAC.

PHYSIOLOGY OF HEARING
• ORGAN OF CORTI IS THE FUNCTONAL UNIT OF HEARING, LODGED ON THE
BASILLAR MEMBRANE.
IT HAS
1. TUNNEL CORTI – GUARDED BY INNER AND OUTER RODS CELLS- FILLED WITH
CORTI LYMPH.
2. HAIR CELLS - 2 TYPEs of HAIR CELLS  INNER & OUTER HAIR CELLS
3. TECTORIAL MEMBRANE – GELATANEOUS MATRIX WITH DELIGATE NERVE FIBRES
4. SUPPORTING CELLS - DIETER’S CELL & HENSEN CELL

• INNER HAIR CELL
• 1 rows
• ~ 3500 cells
• Flask shaped
• Supplied with afferent nerve fibers
• High resistant
• Carries the nerve impulse to the auditory nerve
• OUTER HAIR CELL
• 3-4 ROWS
• ~12000 cells
• Cylindrical shape
• Efferent nerve endings
• Less registrant
• Modulation of transduction

1. CONDUCTION
• Sound waves  pinna– EAC  TMM--IS - SCALA VESTIBULE HELICOTREMASCALA TYMPANI SECONDARY TM.
2. TRANSDUCTION
VIBRATION / HYDROULIC PRESSURESCALA MEDIA BASILLAR MEMBRANE OUTER HAIR CELL CILLIA SHEARS OR STIMULATES
THE TECTORIAL MEMBRANECONVESION OF MECHANICAL ENERGY TO ELECTRICAL ENERGY TRANSMISSION TO THE INNER HAIR
CELL WHICH CARRIES THE NERVE IMPULSE TO AUDITORY CENTER THROUGH THE VIII TH NERVE.
3. NEURAL PATH WAY E. COLI MA
EIGHTH NERVE
COCHLEAR NEUCLEUS
OLIVERY COMPLEX
LATERAL LEMINISCUS
INFERRIOR COLLICULUS
MEDIAL GENICULATED BODY
AUDITORY CORTEX AREA 41 BROCAS AREA---- HEARING PERCEPTION
HEARING PROCESS

STRUCTURES RELATED TO CONDUCTION AND
TRANSDUCTION & BALANCE

AUDITORY NEURAL PATH WAY

• BALANCE
FUNCTIONAL UNIT
1. CRISTA AMPULARIS – SCC.
2. MACULA OF UTRICLE AND SACCULE
CRISTAE
Crest like- mound shaped connective tissue– lodges sensory epithelial cells—cilia of sensory epithelium projects to
the cupula, a gelatinous mass movement of endo lymph  causes movement of cilia.
MACULA ( UTRICLE & SACCULE)
SENSORI NEURO EPITHELIUM—TYPE I & II HAIR CELLS
OTOLITHIC MEMBRANE LODGES THE CRYSTALS OF CALCIUMCARBONATE– OTOLITH
The cilia of hair cells projects to the otolithic membrane and the crystals stimulates the hairs cells in response to
the change in plane .

• HAIR CELLS OF MACULA AND
CRISTA
TYPE I
Flask shaped
Has 1 thick and long kinocilia
Has many thin small stereocilia
Supplied with a single cup shaped nerve ending all base of the
hair cell
TYPE II
Cylindrical in shape
Has 1 thick and long kinocilia
Has many thin small stereocilia
Supplied with 2-3 nerve endings all around base of the hair cell

Ear Anatomy and Physiology Guide by Dr. Tarun Kumar Dwibedi

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