anatomy of ear

2. TEMPORAL BONE
TEMPORAL
BONE
SQUAMOUS PART
PETROUS
PART
TYMPANIC
PART
STYLOID
PART

3. SQUAMOUS PART
 Temporal Surface
 Supramastoid Crest
 Temporalis attachment
 Squamomastoid Suture
 Suprameatal Triangle
 Suprameatal Spine (1.25 cm)
 Cerebral Surface
 Temporal lobe convolutions
 Middle Meningeal Vessel
Grooves
 Articulations
 Parietal Bone—Superiorly
 Mastoid Part–Posteriorly
 Greater Wing-Anteroinferiorly

4.  Zygomatic Process
 Forwards from lower squama
 Triangular Base
 Attaches Lateral temporomandibular Lig.
 Upper border-continues with Supramastoid Crest
 Articular Tubercle
 Mandibular Fossa
 Articular Area- Squamous Part
 Temporomandibular Articulation
 Non Articular Area- Tympanic Part
 Part Of Parotid Gland
 Post-glenoid Tubercle
 B/W Articular Surface & Tympanic Plate
 Prevents backward displacement of mandibular condyle

5. PETROMASTOID PART
 Mastoid Part
 Petrous Part

6.  Petrous Part
 Base—Petrosquamous Suture
 Apex—Greater wing of sphenoid & Basioccipital bone
 3 Surfaces
 Anterior—Inferior temporal gyri, Trigeminal Ganglion
 Posterior—Internal Acoustic Meatus, Endolymphatic Sac
 Inferior—
 Levator veli palatini
 Cartilaginous auditory tube,
 Carotid Canal,
 Jugular Fossa Mastoid CanaliculusVagal Auricular Br.
 Cochlear Canaliculus Anteromedially
 Perilymphatic Duct, Duramater, Vein from Cochlea to IJV

7. TYMPANIC PART
 Fuses with petromastoid
part & squama
 Posterior surface forms
 Anterior wall
 Floor
 Part Of EAM
 Medially—Tympanic Sulcus
 Centrally—Perforated
 Stylomastoid Foramen
 Facial Nerve
 Stylomastoid Artery

8. STYLOID PART
 Slender
 Pointed
 2.5 cm length
 Proximal Part(Tympanohyal)
 Ensheathed by Tympanic Plate
 Distal Part(Stylohyal)
 Muscular Attachments
 Relations
 Lateral:- Parotid Gland
 Base:- Facial Nerve
 Tip:- External Carotid Artery
 Medially:- Stylopharyngeus & IJV

9. BASIC DIVISIONS OF EAR
EXTERNAL EAR MIDDLE
EAR
INNER
EAR

10. EXTERNAL EAR

11. AURICL
E
Prominences
&
Depressions
Ligaments

12. AURICULAR MUSCLES
EXTRINSIC INTRINSIC
 3 in number
 Auricularis Anterior
 Auricularis Superior
 Auricularis Posterior
 6 in number
 Helicis major
 Helicis minor
 Tragicus
 Antitragicus
 Transversus auriculæ
 Obliquus auriculæ

13. NERVE SUPPLY
 Greater Auricular Nerve
 Lesser Occipital Nerve
 Auricular Nerve
 Auriculotemporal Nerve
 Facial Nerve

14. EXTERNAL AUDITORY CANAL
 From Concha to T.M.
 Length24mm
 Cartilaginous-8mm
 Bony-16mm
 2 Suture Lines
 Tympanosquamous
 Tympanomastoid
 Medial End-Tympanic Sulcus

15. RELATIONS OF THE E.A.C.

16. BLOOD SUPPLY OF E.A.C.
 Auricular Br. Of Superficial Temporal Artery
 Deep Auricular Br. Of Maxillary Artery {1st Part}
 Auricular Br. Of Posterior Auricular Artery

17. MIDDLE EAR CLEFT
 Tympanic Cavity
 Eustachian Tube
 Mastoid Air Cell System

18. TYMPANIC CAVITY
 Compartments
 Epitympanum
 Mesotympanum
 Hypotympanum
 Boundaries
 Lateral Wall
 Roof
 Floor
 Anterior Wall
 Medial Wall
 Posterior Wall

19. COMPARTMENTS
EPITYMPANUM
MESOTYMPANUM
HYPOTYMPANUM

20. THE LATERAL WALL
 Wedge Shaped
 3 Divisions
 Bony Lateral Wall Of Epitympanum
 Tympanic Membrane
 Bony Lateral Wall Of Hypotympanum
 3 Holes
 Petrotympanic fissure
 Anterior Canaliculus
 Posterior Canaliculus

22. TYMPANIC MEMBRANE
 Forms lateral wall
centrally
 Oval Shaped
 55° Angle with floor
 Longest Dia.
 -10 mm(P.S.-A.I.)
 Two Divisions
 Pars Flaccida
 Pars Tensa

23.  3 LAYERS OF T.M.
 Outer- Outer Epithelial Layer
 Middle- Lamina Propria (Fibrous Layer)
 Inner- Mucosal Layer
 BLOOD SUPPLY OF T.M.
 Epidermal vessels- Deep Auricular Br. Of Maxillary A.
 Extensive anastomosis- In Lamina Propria
 Mucosal vessels
 Anterior Tympanic Br.- Maxillary A.
 Stylomastoid Br.- Post. Auricular A.

24. CHORDA TYMPANI

25. COURSE & RELATIONS IN TYMPANIC CAVITY
Posterior
Canaliculs
Posterior
Canal Wall
Tympanic
Membrane
Anterior
Canaliculus
Petrotympanic
fissure
FACIAL
NERVE
LINGUAL
NERVE

26. THE ROOF

27. THE FLOOR
 Jugular Wall
 Thickness- Related to
Jugular Fossa Height
 Tympanic Br. Of CN IX
JUGULAR WALL
JUGULAR BULB
HYPOTYMPANUM

28. THE ANTERIOR WALL
 Carotid Wall
 3 Parts
 Upper 1/3rd :- Canal Of Tensor Tympani,
Anterior epitympanic sinus
 Middle 1/3rd :- Tympanic orifice of Eustachian Tube
 Lower 1/3rd :- Superior & Inferior Caroticotympanic N.,
Tympanic Br. Of ICA

29. THE MEDIAL WALL

30.  Promontory
 Basal Coil Of Cochlea
 Tympanic plexus nerves
 Oval Window
 Behind & Above Promontory
 Kidney Shaped
 3.25mm long
 1.75mm wide
 Connects to Vestibule
 Stapes footplate & Annular Lig.

31.  Round Window:-
 Below & behind Oval Window
 Subiculum
 Ponticulus
 Triangular shaped
 Sinus Tympani
 Covering Membrane-
 oval, 2.3 x 1.9mm

32.  Facial Canal aka Fallopian Canal
 Antero-posteriorly above Oval Window & Promontory
 Processus Cochleariformis—Anterior Landmark
 Tensor Tympani tendon attachment

33. THE POSTERIOR WALL
 Aditus Ad AntrumOpening to Mastoid Antrum
 Fossa Incudis Contain Short Process Of Incus & It’s
Suspensory Ligament
 Pyramid Attaches Stapedius & It’s tendon

34. CONTENTS OF TYMPANIC CAVITY
 Ossicles3
 Muscles2
 Chorda Tympani N.
 Tympanic Plexus
 Mucosal Folds
 Blood Vessels

35. OSSICLES

37. MUSCLES
 Stapedius
 Tensor
Tympani

38. MUCOSAL FOLDS OF TYMPANIC CAVITY
Mucus secreting respiratory mucosa with cilia
3 Mucociliary Pathways
Epitympanic
Promontorial
Hypotympanic

39. EMBRYOLOGY REVIEW
PRIMITIVE
TYMPANIC
CAVITY
SACCUS
ANTICUS
SACCUS
MEDIUS
SACCUS
SUPERIOR
SACCUS
POSTICUS
4 POUCHES
BUD OUT

40. Mesotympanum & Epitympanum Seperated By
TENSOR FOLDS
INTEROSSEUS FOLD
MEDIAL INCUDAL FOLD

41. Lateral View:- (13) Tensor Folds, (14) Anterior Malleolar Fold, (39) Tensor Tympani
Tendon, (17) Interosseous Fold, (9) Medial Incudal Fold, (23) Superior Malleal
Ligament, (11) Superior Incudal Fold, (24) Posterior Incudal Fold

42. Inferior View: Tensor Fold (13), The Interosseous Fold (17), The Medial Incudal Fold (9), Isthmus
Tympani Anticus (20), Isthmus Tympani Oticus (21), (5) Obturatoria Stapedis, (8) Plica
Stapedis; (11) Superior Incudal Fold, (14) Anterior Malleal Fold, (18) Superior Malleal Fold,
(19) Incisura Tensoris, (22) Anterior Malleal Ligament, (23) Superior Malleal
Ligament, (24) Posterior Incudal Ligament, (28) Pyramidal Eminence, (39) Tensor Tympani Tendon.

43. ISTHMUS TYMPANI
 Narrow elongated space
 Medially
 Facial Nerve Canal
 Lateral SCC
 Divided by Long Process Of Incus
 Isthmus Tympani Anticus
 Isthmus Tympani Posticus

44. Prussack’s Space
 Boundaries:
 Medially: Neck Of Malleus
 Laterally: Pars Flaccida
 Inferiorly: Lateral Process Of Malleus
 Superiorly: Lateral Malleolar Fold
 Posteriorly: Posterior Malleolar Fold
 Clinical Significance:
 Pars flaccida acquired cholesteatoma formation

45. SPRE AD OF CHOLE STE ATOMA FROM PRUSSAK ’ S SPACE

46. PATTERN OF SPREAD OF CHOLESTEATOMA
Posterior Epitympanum
(Through Superior Incudal Space)
Posterior Mesotympanum
(Through Posterior Pouch Of Von Tröltsch)
Anterior Epitympanum
(Anterior to head of malleus to Supratubal recess)

47. EUSTACHIAN TUBE
Bony Part (Lateral 1/3rd)
12mm , Rectangular opening
Cartilaginous (Medial 2/3rd)
24mm
Torus Tubaris
Blood Supply
Ascending Pharyngeal A.
Middle Meningeal A.

49.  Functions:
 Pressure Equalization
 Mucociliary Clearance & Drainage
 Protection of middle ear from nasopharyngeal
environment & loud sounds

50. IMPROPER FUNCTIONING OF EUSTACHIAN
TUBE
Recurrent URTI, Enlarged Adenoids
Larger Diameter & Shorter Length
Malfunctioning of Tubal Muscles
Reduction in Size Of Ostmann’s Fat Pad
Atrophy Of Tensor Veli Palatini
Collagen Diseases
Loss Of Ciliated Epithelium
Abonormally Thick & Tenacious Secretions

51. MASTOID AIR CELL SYSTEM
 Lies in Petrous Bone
 Volume2mL
1. The Posterosuperior Tract
2. The Posteromedial Tract
3. The Subarcuate Tract
4. The Perilabyrinthine Tract
5. The Peritubal Tract

52. MASTOID AIR CELLS
1. Zygomatic Cells
2. Perilabyrinthine Cells
3. Squamosal Cells
4. Tegmental Cells
5. Sinodural Cells
6. Periantral Cells
7. Marginal Cells
8. Retrofacial Cells
9. Tip Cells
10. Peritubal Cells

53. SURGICAL IMPORTANCE
Surgical Anatomical Reasons
Choice Of Surgical Technique

54. RELATIONS OF THE MASTOID ANTRUM[RT.]

55. INTERNAL EAR

56.  2 Parts:-
 Bony Labyrinth
 Membranous Labyrinth
 2 Types Of Fluids:-
 Perilymph
 Similarity with ECF
 Rich in Na+
 Communicates with CSF-Aqueduct Of Cochlea
 Endolymph
 Similarity with ICF
 Rich in K+
 Secreted by
 Secretory Cells Of Striae Vascularis Of Cochlea
 Dark Cells In Utricle & Ampulla Of SCC

57. BONY LABYRINTH
 Vestibule
 Sphericle Recess
 Saccule
 Elliptical Recess
 Utricle
 Aqueduct Of Vestibule
 Endolymphatic Duct
 5 Openings of SCC
 Semicircular Canals
 Lat., Post., Sup.
 Ampulated & Non-Ampulated Ends
 Crus Commune
 Cochlea

58. MEMBRANOUS LABYRINTH
 Cochlear Duct
 Scala Media
 Utricle & Saccule
 Receives Openings of
SCC
 Macula
 Linear acceleration &
deceleration
 Semicircular Ducts
 Endolymphatic Duct &
Sac

59. THE COCHLEAR SYSTEM

60. Sound Pressure Waves
Through Cochlea
“ORGAN OF CORTI”
Analysis of Waves
Discharge Pattern Of Auditory Nerve
Fibres

61. MODIOLUS
 Coiled By Cochlear
 2.5 coils
 Spiral Ganglion
 Bipolar neurones
 Cochlear nerve
Blue—Low Frequency
Green—Middle Frequency
Red—High Frequency

62. COCHLEAR DUCT
ST
SM
SV
“ORGAN OF CORTI”
STRIA VASCULARIS
REISSNER’S MEMBRANE
BASILAR MEMBRANE

63. ORGAN OF CORTI
 Rests on Basilar Memb.
 From Spiral Limbus To Claudius Cells

64. STRIA VASCULARIS
 3 Layers:
 Outer—Spiral Ligament
 Middle—Intermediate Cells
 Inner—Marginal Cells with Tight Junctions
 Ion pumps, Enzymes, Transport proteins in outer layer
 Homeostatic mechanism of the cochlear fluid
REISSENER’S MEMBRANE
 2 Layers joined with tight junctions
 Impermeable Barrier

65. CELLULAR ARCHITECTURE
 SENSORY CELLS
 Outer Hair Cells
 Inner Hair Cells
 PILLAR CELLS
 Inner Pillar Cells
 Outer Pillar Cells
 SUPPORTING CELLS
 FOR IHCs Inner Phalangeal Cells, Border Cells
 FOR OHCs  Deiter’s Cells

66. Inner Hair Cell Outer Hair Cell
 Single Longitudinal Row
 Located on the inner side of
sensory region
 3-5 Layers
 Located on the outer side of
sensory region

67.  Function of Organ Of Corti:
Mechanoelectrical Transduction
Neural Signalling IHCs
Amplification of sound waves OHCs
Transmission to Auditory Nerve & Higher Centres

68. OHC--ULTRASTRUCTURE
 2 Ends:-
 Apical End
 Sensory part with stereocilia
 Flattened
 Basal End
 Synaptic Pole
 Stereocilia:-
 W or V Pattern
 3-5 Rows
 Cylindrical
 Angled towards each other
 Tip Links

69.  Dense Rootlets
 Tropomyosin with actin
filaments
 Stereociliary Membrane
 Calcium controlling
proteins
 Ion Channels
 Deflections Of Hair
Bundle Controls the
opening & Closing of ion
channels

70. DEFLECTION
OF HAIR
BUNDLE
In Stereociliary height
Against stereociliary
height
Depolarizes OHC
Hyperpolarizes OHC

71. IHC--ULTRASTRUCTURE
 Flask Shaped Body
 3-4 rows of stereocilia
 Height increases in stepwise manner
 Cellular structure similar to OHC
 Deflections brought by
 Sound induced motions of B.M.
 Endolymphatic fluid motion
 Depolarization of IHC
 Release of Amino Acid Glutamate
 Calcium Mediated

72. THE ASCENDING AUDITORY PATHWAYS
 Major components are:-
 The Cochlear Nuclear Complex
 The Superior Olivary Complex
 Inferior Colliculus
 Medial Geniculate Body
 Auditory Cortex