This document provides an overview of the anatomy of the ear in 3 parts: 1. The external ear which includes the pinna and external auditory meatus leading to the tympanic membrane. 2. The middle ear which is an air filled cavity containing the 3 ossicles (malleus, incus, stapes) that transmit sound vibrations from the tympanic membrane to the inner ear. 3. The inner ear which contains the bony and fluid filled labyrinth involved in hearing and balance. Each section describes the structures and their functions. Clinical correlations regarding common ear diseases are also discussed.

1. 1
THE EAR
Major Rahul Jha
Graded Specialist
Anatomy
ACMS

2. Introduction
• Organ of hearing and also plays an important role in
equilibrium.
• Divided into three parts:-
– External ear.
– Middle ear.
– Internal ear.
• External ear consists of Pinna/auricle.
• Tympanic membrane at the medial end of EAM.
• Middle ear – an air filled space containing ear ossicles.
• Communicates with the nasopharynx through auditory
tube.
• Internal ear consists of bony labyrinth & fluid filled
labyrinth.
2

3. 3
THE EAR

4. EXTERNAL EAR
Components
–Pinna
–EAM
–Concerned with reception
of noise.
4

5. EXTERNAL AUDITORY MEATUS
5

6. 6
EXTERNAL AUDITORY MEATUS
• Length: 2.5 cms
• Parts
– Cartilagenous : lateral 1/3rd
– Bony: medial 2/3rd
Bends
– B/T lat 1/3rd
& medial 2/3rd
– 5 mm from TM
Direction
– Backwards & medially
• To examine, pull ear.
LAT
MED

7. 7
EAMEpithelium
– Adherent to bone & cartilage
– Ceruminous glands
– Secretions prevent entry of bacteria, make it waterproof
Blood supply
– Ant tympanic
– Deep auricular
– Post auricular
Nerve supply
Medial 1/4:
• IX CN
• Auricular br of X CN (Arnold’s)
Lateral 3/4:
• Roof: ATN
• Floor: Great auricular N

8. Tympanic membrane
• Thin semi-transparent membrane which forms
the partition between the EAM & the middle ear.
• Placed obliquely at an angle of 55 degrees with
the floor.
• Faces forward, downward & laterally.
8
TYMPANIC MEMBRANE

9. 11
Angle of TM to EAM

10. 12
TYMPANIC MEMBRANE
Subdivisions
• By malleolar folds
– Pars flaccida (Shrapnel’s membrane)
• Present between folds
• Lax area
– Pars tensa
• Rest of membrane
• Tense due to
– Attachment of handle of malleus
– Radiating fibres of intermediate layer PF
PT
AMF
PMF
Line of attach of handle of malleus
on medial surface

11. 13
TYMPANIC MEMBRANE
Surfaces
Lateral surface
• Concave, directed down, forward & laterally
Medial surface
• Convex, max at umbo
• Handle of malleus attached here
• Chorda tympani is medial to handle of malleus

12. 14
Structure
From lateral to medial
Outer cuticular layer
• Lined by str squamous nonkeratinized epithelium
Intermediate fibrous layer
• Outer radiating, inner circular fibres
Inner mucous layer
• Lined by columnar epithelium with patchy ciliated
Handle of malleus & chorda tympani lie b/t mucous &
intermediate fibrous layer
TYMPANIC MEMBRANE

13. 15
Outer cuticular layer
Middle fibrous layer
Inner mucous layer
Deep circular
fibres
Superficial
Radiating fibres
Pars flaccida
TM: STRUCTURE

14. 16

15. 17
Nerve Supply
– Lateral surface
– ATN
– Vagus N (auricular br)
– Medial surface
• IX CN (tympanic br-Jacobson’s N)
• Chorda tympani
Blood Supply
– Deep auricular br of maxillary (lateral surface)
– Ant tympanic Ar
– Post auricular: stylomastoid br
TYMPANIC MEMBRANE

16. 18
CLINICAL ANATOMY
• ASOM
– Pus discharged laterally
• Myringotomy
• Incision at posteroinferior quadrant
–Prevent damage to chorda tympani
–Rich blood supply: healing faster

17. 19
AUDITORY OSSICLES

18. 20
MALLEUS
• Head
– In epitympanic recess
– Post surface: facet for incus-
Incudomalleal jt: Saddle jt
• Neck
– against pars flaccida
– Chorda tympani cross medial
to neck
• Handle
– Project down & back till umbo
– processes
• lateral pr : Upper end, handle &
lat pr attached to fibrous layer of
TM, malleolar folds
• Anterior pr : attachment of ant
lig of malleus

19. 21
INCUS
Body
• In epitympanic recess
• Articulates anteriorly with
head of malleus
Short process
• Lig attached to fossa
incudis (post wall of TC)
Long process
• Hook medially, articulate
with stapes
• Incudostapedial joint: ball
& socket

20. 22
STAPES
• Head
– Articulates with lenticular
nodule of incus
• Neck
– Stapedius attached to back
of neck
• Ant & post limbs
• Foot plate
– anchored to fenestra
vestibuli by annular lig
– syndesmosis

21. 23
MIDDLE EAR
Biconcave box like cavity
Location
– Petrous temporal bone
Parts
– Roof
– Floor
– Walls
• Anterior & Posterior
• Medial & Lateral

22. 24
Canal for T T
Auditory tube
Aditus to antrum
Mastoid antrum
Mastoid cells
Mastoid process
EAM
Middle ear (Tympanic cavity)
MIDDLE EAR
Ht & Length: 15 mm
Medial & lateral walls: 2 mm
Roof: 6 mm
Floor: 4 mm

23. 25
Auditory tube
Tegmen tympani Aditus to antrum
Mastoid antrum
Mastoid air cells
Mastoid process
Middle
Ear
ANT & POST WALLS & ROOF

24. 26
Epitympanic
recess
Aditus
Auditory tube
ICA
Sup bulb of IJV
VII CN
ROOF & FLOOR

25. 27
Auditory tube
Cochlea
Semicircular canal
Middle ear
Tympanic antrum
Vestibule
Stapes
Tympanic membrane
EAM Internal acoustic meatus
Inner
ear
LATERAL & MEDIAL WALLS

26. 28
LATERAL & MEDIAL WALLS

27. 29
MEDIAL WALL

28. 30
MIDDLE EAR: COMMUNICATIONS
Anterior wall
• auditory tube
Posterior wall
• mastoid antrum
Medial wall
• inner ear
Lateral wall
• tympanic membrane

29. 31
Left ear: TM removed
Roof
Floor
Medial wall
Ant
wall
Post
wall

30. 32
MIDDLE EAR: WALLS & FEATURES

31. 33
Formed by
– Tegmen tympani
• Thin bony plate of petrous temporal
• Separates tympanic cavity from MCF
• Pierced by lesser & greater petrosal nerves
Applied
– If unossified: spread of infection to meninges
– Venous drainage to superior petrosal sinus through
petrosquamous suture: infection to sinus
ROOF

32. 34
Petrous temporal
ROOF

33. 35
MIDDLE EAR: ROOF

34. 36
FLOOR
Formed by
– Plate of bone above jugular fossa
Relations
– Anterior
• Carotid canal
– Posterior
• IJV
Tympanic canaliculus - tympanic br of IX CN enters
Applied
– Spread of infection to IJV: thrombosis

35. 37
Epitympanic
recess
Aditus
Auditory tube
ICA
Sup bulb of IJV
VII CN
MIDDLE EAR: FLOOR

36. 38
ANTERIOR WALL
Shortened by approximation of roof & floor
Anteriorly has post wall of carotid canal
Features
– Canal for
• Tensor tympani
• Auditory tube
– Processus trochleariformis
• Bony shelf extends back on medial wall & turns lateral:
provide pulley for tensor tympani to get attached to
handle of malleus

37. 39
POSTERIOR WALL
Wider above than below
Features
1. Aditus to mastoid antrum
• Epitympanic part communicate with mastoid antrum
1. Facial canal: in lower part
2. Pyramid
• Projects above facial canal
• Contains stapedius, from apex tendon

38. 40
Left ear, TM removed
Roof
Floor
Medial wall
Ant
wall
Post
wall

39. 41
LATERAL WALL
Components
Tympanic Membrane
Epitympanic recess
• Part above tympanic cavity
– Contains
» Upper half of malleus
» Greater part of incus

40. 42
MEDIAL WALL
Features
1. Promontory
• Due to basal turn of cochlea
• Tympanic plexus (IX CN)
1. Fenestra vestibuli (fossa ovalis)
• Behind & above promontory
• Closed by base of stapes & annular ligament
1. Fenestra cochleae (fossa rotunda)
• Below & behind promontory
• Closed by secondary TM (separate TC from scala tympani)
1. Sinus tympani
• Depression behind promontory
• Position of ampulla of post semicircular canal
1. Facial canal
• Oblique part, run back & down above fenestra vestibuli
1. Processus trochleariformis

41. 43
Posterior
Left ear, TM removed
roof
floor
Medial wall
Ant
wall
Post
wall

42. 44
MEDIAL WALL

43. MEDIAL WALL

44. 46
MIDDLE EAR: MUSCLES

45. 47
TENSOR TYMPANI
Origin
• Bony & cart part of AT, becomes tendon, hooks around
processus trochleariformis
Insertion
• Handle of malleus: upper part
N/S
• Nerve to Medial pterygoid
Actions
• Pull handle of malleus, TM concave, makes tense
• Increase tight adhesion of footplate to fenestra vestibuli
– Hence dampens sound

46. 48
STAPEDIUS
Origin
• Interior of hollow pyramid
Insertion
• Back of neck of stapes
N/S
• Facial nerve
Actions
• Retract neck of stapes from fenestra vestibuli
• Paralysis: hyperacusis

47. 49
CLINICAL ANATOMY
1. Otitis media
2. Otosclerosis
3. Injury to nerve to stapedius
• Hyperacusis

48. 50
Normal TM Wax
CLINICAL ANATOMY

49. 51
Serous otitis media
ASOM
CLINICAL ANATOMY

50. 52
Perforation Tympanosclerosis
CLINICAL ANATOMY

51. 53
PERFORATIONS

52. 54
OTITIS EXTERNA

53. 55
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