Anatomy of ear includes External ear, Middle ear & Inner ear

1. BY
Dr.K.AMRITHAANILKUMAR
PRESENTS

3. Kural 411
செல்வத்துட் செல்வஞ் செவிச்செல்வம் அச்செல்வம்
செல்வத்து செல்லாந் தலல.
TRANSLATION
Wealth of wealth is wealth acquired be ear attent;
Wealth mid all wealth supremely excellent.
EXPLANATION :
Wealth (gained) by the ear is wealth of
wealth; that wealth is
the chief of all wealth.

4. EXERNAL EAR

5. • Ear is divided into
»1. external ear
»2. Middle ear
»3. internal ear

6. 1.External ear
• Auricle/pinna
• External acoustic canal/ auditory
canal
• Tympanic membrane/ drum head

7. Auricle/pinna

8. External acoustic canal
• It is 24mm, not a straight tube- so
pinna has to be pulled upwards,
backwards & laterally
• It has 2 parts

9. Cartilaginous part -8mm Bony part – 16mm
 2 deficiencies- “fissure of
santorini”(parotid and
superficial mastoid
infection will appear )
Ceruminous & pilosebaceous
glands – wax
Has hair follicles ( prone to
furuncle )
 Lateral – isthumus( foreign
bodies gets lodged )& antero
inferior –anterior recess &
foramen of huscke (4 yrs/
adult – parotid transmit
infections )
Devoid of hair & ceruminous
glands

11. Tympanic membrane /
drum head
• Pearly white semi translucent
membrane
• It has 2 parts – pars tensa & pars
flaccida

12. Tympanic membrane /
drum head
• Pars tensa
–periphery fibrocartilaginous ring
called annulus tympanicus,
deficient in the pars flaccida called
notch of rivinus & inwards tented
inwards called umbo
• Pars flaccida/shrapnells membrane
–situated above the lateral process
of malleus

14. Nerve supply to tympanic
membrane
• Anterior ½ - auriculotemporal
nerve
• Posterior ½ - auricular branch of
vagus nerve
• Medial branch – tympanic branch
of glossopharyngeal nerve (
Jacobson neve )

16. Relations
• Superior –middle cranial fossa
• Posterior –mastoid air cells &
facial nerve ; p.superior –mastoid
antrum ( acute mastoiditis)
• Anterior -temporomandibular joint
• Inferior -parotid gland

17. Nerve supply
• Herpes zoster oticus – occur in
facial neve ( concha & posterior
part of tympanic membrane )

19. CLINICAL ANATOMY OF
EXTERNAL EAR
1. Perichondritis pinna
- inflammation of
perichondrium
with pus between
perichondrium
&cartilage
- Pinna totally deformed
Like cauliflower

20. 2. Otitis externa
Acute inflammation of skin lining
EAC
Infective
- Bacterial – furuncle
- Fungal –otomycosis
- Viral – herpes zoster
oticus
Reactive
- Eczematous
- Seborrheic
- neurodermitis

21. 3. Otomycosis
- Fungal infection
affecting
external ear
- Predisposes
Diabetes &
immunocompromised
- Infect. Org
Aspergillus niger

22. 4. Furunculosis
-Inflammation of hair follicles
May spread
- Subcutaneously
Cause -- cellulitis
- Infect. Org
1. Staphylococus
2. pseudomonas
3. proteus

23. 5. Cerumen/Miscellaneous wax
Mixture of ceruminous
& sebaceous gland
with desquamated
Epithelium in EAC
Functions
- Antibacterial
- trap dust
- foreign body

24. MIDDLE EAR

25. 2.Middle ear
Includes ,
• Eustachian tube
• Tympanic cavity
• Aditus
• Mastoid air cells

26. Eustachian tube
• It is 36 mm long in adults
• Enters nasopharynx 1.25 cm
behind posterior end of inferior
turbinate
• Lateral 1/3- bony
• Medial 2/3 – fibrocartilaginous
• Junction - isthumus , narrowest
part of ET

28. Anatomy of cartilagenous
part
• It lies posteromedially
• Consists of medial and lateral
lamina seperated by a elastic
hinge
• Anterolaterally – ostmanns fat pad

31. Blood supply
• Ascending pharyngeal artery
• Middle meningeal artery
• Artery of pterygoid canal
• Veins – pterygoid venous
plexuses

33. Tympanic cavity
Includes
• Epi tympanium
• Meso tympanium
• Hypo tympanium

34. Walls of Tympanic cavity

35. • Roof
• Thin plate of bone called tegmen
tympani , separates he tympanic cavity
from middle cranial fossa
• Extends posteriorly to form roof of the
aditus and antrum
• Floor
• Thin plate of bone separates tympanic
cavity from the jugular bulb
• Medial border – tympanic branch of the
glossopharyngeal nerve ( IX) enters
middle ear

37. • Anterior wall
• Thin plate of bone separates the
cavity from internal carotid artery
• Lateral wall
• Membranous - tympanic membrane
• Bony - lateral attic wall
above pars flaccida
Lateral wall of hypo
tympanum

38. Lateral wall

39. Medial wall
It has
• Promontory
• Oval window
• Round window
• Tympanic part of bony facial nerve
canal
• Lateral semicircular canal
• Processes cochleaformis

41. • Promontory
• is a round elevation occupying much of
central portion of medial wall
• formed by basal turn of cochlea
• usually as small grooves on its surface
containing the nerves which form the
tympanic plexuses

43. Oval window
• Lies behind & above he promontory
• A kidney shaped opening that connects
the tympanic cavity with the vestibule
• Close by footplate of stapes
• Size – 3.25mm long & 1.75 mm wide

45. Round window
• 2.3 X 1.9 , placed right angle to the
foot plate of stapes
• Lies below & behind the oval window
• Separate by subiculum ( post extension
of promontory)
• Ponticulus – another ridge above
subiculum & runs to pyramid on
posterior wall
• Sinus tympani – where the ponticulus
& subiculum meet

46. Facial nerve canal
• Facial nerve canal ( fallopian canal ) runs above
the promontory and oval window in an
anteroposterior direction
• Anterior – processus cochlariformis , a curved
projection of bone it anteriorly houses the tendon
of tensor tympani muscle & laterally to the handle
of malleus
• Above – forms the medial wall of epi tympanum
• Behind --facial canal starts to turn inferiorly as it
begins to descent the posterior wall of tympanic
cavity
• Posterio lateral - The dome of lateral semicircular
canal (posterior portion of epitympanium),

50. posterior wall
• Aditus & antrum
• Fossa incudes for short process of incus
• Bulge produced by lateral semicircular
canal
• Pyramidal eminence for stapedius tendon
• Bulge produced by vertical part of facial
nerve
• Sinus tympani
• Facial recess

52. Posterior wall
• Upper part – large irregular opening – the
aditus and antrum that leads back from the
posterior epitympanium into mastoid
antrum
below
Small depression , fossa incudis ,houses the
short process of incus & suspensory ligament
below
Opening in chorda tympani nerve is Pyramid,
a small hollow conical projection with its
apex pointing anteriorly

53. facial recess
• Is a groove which lies between
pyramid with facial nerve & annulus
of tympanic membrane
• Bounded by
• Medially – facial nerve
• Laterally – tympanic annulus
• Obliquely – chorda tympani nerve
running between 2

55. sinus tympani
• Bounded by
• Superior – ponticulus
• Inferior - subiculum
• Lateral - mastoid segment of facial
nerve
• Medial - posterior semicircular
canal
• Site for – cholesteatoma recurrence

57. contents of middle ear
cavity• Air
• 3 ossicles – malleus, incus, & stapes
• 2 muscles – tensor tympani &
stapedius
• 2 nerves - chondral tympani &
tympanic plexus
• Mucosal folds & ligaments
• Blood vessels

59. Muscles of middle ear

61. Chorda tympani nerve
• Enters tympanic cavity from posterior
canaliculus at the junction of lateral and
posterior wall
• Runs across medial surface of Tympanic
membrane btn mucosal & fibrous layers
• Passes medial to upper portion of the handle
of malleus
• Leaves through petro tympanic fissure
• Carries taste sensation from anterior 2/3 from
same side of tongue & secretomotor fibres to
submandibular gland

63. Tympanic plexus
• Formed by
• Tympanic branch of glossopharyngeal
nerve ( jacobsons nerve )
• Caroticotmpanic nerves , arise from
sympathetic plexus around internal
carotid artery

65. • Nerves form plexuses on promontory &
provide branches to mucous membrane
lining the tympanic cavity , Eustachian
tube, mastoid antrum & air cells
• Plexus provide branches to join the
greater superficial petrosal nerve &
lesser superficial petrosal nerve
contains all the parasympathetic fibres
of the glossopharyngeal nerve.

66. Mastoid air cells
• Interconnected & lined by squamous
non – ciliated epithelium
• Mastoid process can be pneumatic ,
sclerosed or mixed
• Mastoid process develops by age of 2
yrs
• Adius & antrum is the opening in
posterior wall of middle ear & leads
posteriorly to antrum

68. Mastoid antrum
• The roof of mastoid antrum ( tegmen
antri ) separate it from middle cranial
fossa
• Lateral - squamous temporal bone
• Medial – posterior & horizontal
semicircular canal
• Posterior – communicate by several
openings with mastoid air cells
• Specific site –MacEwen’s triangle

69. Macewens triangle
• superior – temporal line
• anterior – posterior – superior margin
of bony external auditory canal
opening
• posterior – tangent drawn to mid –
point of posterior wall of external
auditory canal
• contain spine of henle
• mastoid antrum lies 12 – 15 mm deep
to triangle

71. mucosa of middle ear cleft
• mucus membrane of the nasopharynx is
continuous with that of middle ear,
aditus , & antrum
• mucus secreting
• respiratory type
• cilia bearing
• lines the bony wall of tympanic cavity &
wraps the middle ear structure –
ossicles , mucosal ligaments ,& nerves
like peritoneum wraps viscera of the
abdomen

72. Blood supply
• arteries
• 2 main – anterior tympanic branch of
maxillary artery
Stylomastoid branch of posterior
auricular artery
• 4 minor – petrosal branch of middle
meningeal artery
Superior tympanic branch of
middle meningeal artery
Branch of artery of pterygoid canal
Tympanic branch of internal carotid
• Veins – pterygoid venous plexuses
Superior petrosal sinus

74. Lymphatic drainage
Area Nodes
• Concha, tragus, fossa
triangularis & external
cartilaginous canal
• lobule and antitragus
• Helix & antihelix
• Middle ear & Eustachian tube
• Inner ear
• Preauricular & parotid nodes
• Infra auricular nodes
• Post auricular nodes, deep
jugular & spinal accessory
nodes
• Retro pharyngeal nodes –
upper jugular chain
• No lymphatics

76. CLINICAL ANATOMY OF MIDDLE
EAR
1. Acute suppurative otitis media
- It is an acute
Inflammation of
Middle ear by pyogenic
Organisms
- Middle ear includes
1. Eustachian tube
2. Middle ear
3. Attic
4. Aditus
5. Antrum & Mastoid
air cells

77. 2. Otitis media with effusion
Syn.- Serous otitis media,secretory
otitis media ,Glue Ear
It is an insidious cndn Characterised by
Accumulation of non-purulent effusion
In the middle ear cleft Effusion is thick & viscid

78. 3. Cholesteatoma
“Skin in wrong Place”
- Middle ear is lined
either by
ciliated columnar
or cuboidal cells.
- But whereas
in cholesteatoma,
it is lined by
Keratinizing Squamous epithelium

79. 4. Chronic suppurative
otitis media
It is a long standing infection of a part or
whole of middle ear cleft Characterized
by ear discharge & permanent
perforation.

80. INNER EAR

81. Inner ear
• It exits within the temporal bone (
petrous bone )
• It is a complex structure . It is located
in a bony cavity called bony labyrinth
• It is filled with a fluid called perilymh ,
which is similar to CSF

82. Bony labryinth

83. Within the bony labyrinth is the
membranous labyrinth

84. Membraneous labyrinth
• Has 2 parts
• semicircular canal – 3 lateral ,
posterior & superior ( crista ampularis )
angular secretion
• utricle & saccule – utricle 5 opening of
semicircular canal ( macula ) linear
acceleration

85. cochlea
• central axis modiolus
• cochlear canal – runs 2 ½ turns
• cochlear duct - Scala vestibule , Scala
tympani , Scala media & organ of corti
openings – fenestra vestibule
& fenestra cochlea
hair cells ( inner & outer )
transduction of mechanical
energy to electrical energy

87. • cochlear canal - divided into Scala
vestibuli & Scala tympani by spiral
lamina & basilar membrane
cochlear duct is within
cochlear canal
receptor of organ hearing –
organ of corti
• organ of corti - specialized organ of
hearing
lies within cochlear duct
on the basilar membrane
contains hair cells –
impulses carried by VII nerve

89. • receptors for balancing – macula (
thickening – in the walls of saccule &
utricle )
crest ( in the
ampulla of semicircular ducts )

90. Basilar membrane
• Forms the floor of scala media
• 35mm long
• Auditory nerve endings are located
in BM
• Organ of corti resides on the BM

92. • Width
• Base ( 0.1 mm ) = narrow & stiff
• Apex (0.5 mm ) = boad / wide &
flaccid
• Opposite to cochlear ducts width
• Reacts more to vibrations of IE than
do most of the other structures.

93. Hair cells
• Hair cells lays down on the fibrous BM
• 3 – 5 rows of 12, 000 o 15, 000 parallel
outer hair cells (OHCs)
• One row of 3, 000 inner hair cells ( IHCs)
• On the top of each hair cells are hair –
like projection called “stereocilia”
• Stereo cilia on the top of OHCs are
embedded in the tectorial membrane

95. The direction in which stereo cilia are
bent during stimulation
• If cilia bend in one direction – nerve
cells are stimulated
• If cilia bend in the other way – nerve
impulses are inhabited
• If cilia bend to the side - no
stimulation at all

96. cochlear microphone
• Resemblance between cochlea &
microphone in their function
• cochlea convers sound waves into an
energy form useful to the auditory nerve
• microphone converts the sound pressure
coming form a speakers mouth into an
alternating electrical current
• This action is called cochlear
microphone (CM )

97. • a result of changes in polarization caused
by the bending back & forth of hair cells
cilia
• for every up & down cycle of BM , there is
an one in & out cycle of stereo cilia of the
OHCs causing them to become
alternatively depolarized & hyper
polarized
• CM can be measured by placing needle
electrode over the RW or within the
cochlea

99. Action potential
• A change in the electrical potential
occurring on the surface of each
neuron after they are being stimulated
by HCs
• Increases in the intensity of the
auditory input signal to the cochlea
result in increased electrical output
from HCs
• This stimulation causes increased
electrical activity in the neuron

100. Transformer action
• It is accomplished by
• Lever action of ossicles : handle of malleus is 13
times longer than long process of incus

101. Hydraulic action of
tympanic membrane
• the area of tympanic membrane is much
larger than the area of stapes footplate . the
average ration is 21:1 .
• the effective vibratory area of tympanic
membrane is only 2/3 rd. , so the effective
area ratio is reduced to 14: 1 .
• this is the mechanical advantage provided by
the tympanic membrane

102. Curved membrane effect
movements of the tympanic membrane
are more at the periphery than at the
centre

103. CLINICAL ANATOMY OF INNER
EAR
1. Benign paroxysmal positional vertigo (BPPV)
- also known
as positional vertigo
- It is a dizzy or spinning
sensation in your head
- most common type
of vertigo.

104. 2. Meniere's disease
causes episodes of vertigo, ringing
in the ears (tinnitus), ear
pressure/fullness and hearing loss.

105. 3. Labyrinthitis and vestibular
neuritis
- occurs when the
Hearing & balance
nerves become inflamed
- resulting in sudden
1. hearing loss
2. balance problems
3. vertigo.

106. 4. Superior semicircular canal dehiscence (SSCD)
- patient has a loss or absence
of the bone that covers
your superior
semicircular canal
Symptoms
1. pressure/
sound-induced vertigo
2. hearing loss
3. ear pressure,
4. hearing your
own breathing and blinking

107. REFERENCES
• Diseases of Ear, Nose and Throat & Head
and Neck Surgery by P L Dhingra
• BD Chaurasia's Human Anatomy Regional
and Applied Dissection and Clinical: Vol. 3:
Head-Neck Brain

108. A
Special
Thank you
To
A
Very
Special Doctor
en love da Homoeopathy