The document provides information on the anatomy of the ear and auditory pathway. It discusses the three parts of the ear - external ear, middle ear, and inner ear. The external ear includes the pinna and external auditory meatus. The middle ear contains the tympanic membrane, three ossicles (malleus, incus, stapes), and two small muscles (tensor tympani and stapedius). The inner ear is made up of the cochlea and vestibular system. The auditory pathway transmits signals from the inner ear to the brainstem and auditory cortex.

1. EAR AND AUDITORY PATHWAY
Maj Rishi Pokhrel
Dept of Anatomy
NAIHS
www.slideshare.net

2. • One structure of human body 0.1 mm
thick and derived from all 3 germ layers?
2

3. 3Cochlea Sec tympanic membrane
Promontory
Middle
ear
Stapes
Semicircular canal
Vestibule
of
inner
ear
THREE PARTS OF EAR
Ext auditory meatus
Tympanic membrane
External ear

4. EXTERNAL EAR
4
• Pinna
• External auditory meatus
PINNA
• Concha
• Helix
• Antihelix
• Scaphoid fossa & triangular
fossa
• Tragus
• Antitragus
• Intertragic notch
• Lobule

5. 5
EXTERNAL EAR

6. EXTERNAL AUDITORY MEATUS
Extends from bottom of concha to TM (Length: 25 mm)
Parts
– Cartilaginous: lateral 1/3rd
– Bony: medial 2/3rd
Bends
– B/T lateral 1/3rd
& medial 2/3rd
– 5 mm from tympanic membrane
Direction
– Backwards & medially
Epithelium (skin)
– Adherent to bone & cartilage
– Ceruminous glands
– Secretions prevent entry of bacteria
6

7. 7
Nerve supply
• ATN (V3)
• Great auricular (C2,3)
•Lesser occipital (C2)
•Facial
•Vagus
•Motor- Facial
Blood supply
•Post auricular
•Superficial temporal
•Ant tympanic
•Deep auricular

8. TYMPANIC MEMBRANE
Size
Diameter – 1cm
Thickness – 0.1 mm
Position
– Lie obliquely 55 deg to EAM
– Faces downward, forward &
laterally
Umbo
– Concavity due to attachment of
handle of malleus
8

9. TYMPANIC MEMBRANE
Subdivisions
– Pars flaccida (Shrapnel’s membrane)
• between folds
• lax area
– Pars tensa
• Rest of the membrane
• tense due to
– attachment of handle of malleus
– radiating fibres of intermediate layer
9
PF
Pars Tensa
AMF
PMF
Line of attach of handle of malleus
on medial surface

10. TYMPANIC MEMBRANE
10
Surfaces
Lateral surface
• Concave, directed down, forward & laterally
Medial surface
• Convex, maximum at umbo
• Handle of malleus attached here
• Chorda tympani is medial to handle of malleus

11. TYMPANIC MEMBRANE
Structure
From lateral to medial
– Outer cuticular layer: stratified squamous nonkeratinized epithelium
– Intermediate fibrous layer: Outer radiating, inner circular fibres
– Inner mucous layer: columnar epithelium; patchy ciliated
Handle of malleus & chorda tympani lie b/t mucous & intermediate fibrous layer
11
Outer cuticular layer
Middle fibrous layer
Inner mucous layer
Deep circular
fibres
Superficial
Radiating fibres
Pars flaccida

12. Tegmen tympani
Tensor tympani
Petrotympanic fissure
Anterior canaliculus
Chorda tympani
Tympanic
membrane
Handle of malleus
Processus
cochleariformis
Aditus
LATERAL WALL OF LT MIDDLE EAR
WITH CONTENTS

13. TYMPANIC MEMBRANE
Nerve supply
– Lateral surface
• ATN
• Vagus (auricular br)
– Medial surface
• IX CN (tympanic br)
• Chorda tympani
Blood supply
– Deep auricular
– Anterior tympanic
– Posterior auricular: stylomastoid br 13

15. CLINICAL ANATOMY
• ASOM
– Pus discharged laterally
• Myringotomy
• Incision at posteroinferior quadrant
–Prevent damage to chorda tympani
–Rich blood supply: healing faster
15

16. MIDDLE EAR
16
Canal for T T
Auditory tube
Aditus to antrum
Mastoid antrum
Mastoid cells
Mastoid process
A P

17. 17
Left ear: TM removed
Roof
Floor
Medial wall
Ant
wall
Post
wall

18. 18

19. ROOF
19
Petrous temporal
Formation
– 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

20. FLOOR
Formation
– Floor of jugular fossa (posteriorly)
– Posterior wall of ascending part of carotid canal (anteriorly)
- Tympanic Canaliculus for tympanic br of IX CN
Applied
– Spread of infection to IJV: thrombosis
20
Epitympanic
recess
Aditus
Auditory tube
ICA
Sup bulb of IJV
VII CN

21. ANTERIOR WALL
• Shortened by approximation of
roof & floor
• Anteriorly shows posterior wall of
carotid canal
• Canal for
• Tensor tympani (above)
• Auditory tube (below)
• Processus trochleariformis
• Bony shelf extends back on
medial wall & turns laterally;
pulley for tensor tympani
21

22. 22

23. POSTERIOR WALL
• Wider above than below
• Aditus to mastoid antrum
• Facial canal
• Pyramid: tendon emerges
from apex
• Posterior Canaliculus of
chorda tympani
23

24. MEDIAL WALL
Promontory: due to basal turn of cochlea
– Tympanic plexus (IX CN) lies over promontory
Oval window (fenestra vestibuli )
– behind & above promontory
– closed by base of stapes & annular ligament
Round window (fenestra cochleae )
– below & behind promontory
– closed by secondary TM
Facial canal: above & behind promontory
– oblique part, run back & down above oval window
Prominence of lateral semicircular canal
– above facial canal
24

25. 25
Left ear: TM removed
Medial wall

26. 26
MEDIAL WALL

27. LATERAL WALL
• Tympanic Membrane
• Epitympanic recess
– Part above tympanic cavity
– Upper half of malleus
– Greater part of incus
27

28. MIDDLE EAR: COMMUNICATIONS
• Anterior wall : auditory tube
• Posterior wall: mastoid antrum
• Medial wall : inner ear
• Lateral wall shows : tympanic membrane
• Roof and floor: none
28

29. EAR OSICLES

30. MALLEUS
Head
In epitympanic recess
Post surface: facet for incus- Incudomalleal joint (saddle)
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
30

31. 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
31

32. 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
32

33. TENSOR TYMPANI
Origin
• Bony & cart part of AT, becomes
tendon, hooks around processus
trochleariformis
Insertion
• Handle of malleus: upper part
Nerve supply
• Nerve to medial pterygoid
Actions
• Pull handle of malleus, TM concave,
makes tense
• Increase tight adhesion of footplate to
fenestra vestibuli
– dampens sound
33

34. STAPEDIUS
Origin
• Interior of hollow pyramid
Insertion
• Back of neck of stapes
Nerve supply
• Facial nerve
Actions
• Retract neck of stapes from fenestra vestibuli
• Paralysis: hyperacusis
34

35. 35

36. 36
CLINICAL ANATOMY
Normal TM Wax

37. 37
PERFORATION OF TM
Perforation

38. MYRINGOTOMY
MYRINGOTOMY & SYRINGING
EAR SYRINGING

39. 39
OTITIS MEDIA
Serous otitis mediaASOM

40. 40
OTITIS EXTERNA

41. TYMPANOSCLEROSIS

42. Internal ear
42

43. 43

44. 44

45. Auditory pathway
45

46. Auditory pathway
46

47. 47

48. Olfactory pathway
48

49. 49

50. 50

51. 51

52. 52

53. 53

54. 54
Olfactory reflexes

55. ? 55