Presentation is loading. Please wait.

Presentation is loading. Please wait.

Anatomy of Ear & Mastoid Dr. Vishal Sharma. Embryology.

Similar presentations


Presentation on theme: "Anatomy of Ear & Mastoid Dr. Vishal Sharma. Embryology."— Presentation transcript:

1 Anatomy of Ear & Mastoid Dr. Vishal Sharma

2 Embryology

3

4

5

6

7

8

9

10

11

12 External ear:  Pinna / auricle  External auditory canal Middle ear cleft:  Eustachian tube  Tympanic cavity (middle ear)  Mastoid air cell system Inner ear (labyrinth):  Cochlea  Vestibule  Semicircular canals Parts of ear

13 External Ear

14

15

16

17

18 External auditory canal 24 mm long; Lateral 1/3 Cartilaginous (8 mm): up + back + medial. Medial 2/3 Bony (16 mm): down + forward + medial. Pinna pulled up + back + lateral to straighten external auditory canal. Only cartilaginous skin has hair follicles: furuncle Cartilaginous fissure of Santorini & bony foramen of Huschke: passage of infection to and from parotid gland

19

20 Nerve supply of E.A.C.

21 Middle ear cleft Consists of: Eustachian tube Tympanic cavity (middle ear) Aditus Mastoid air cell system Develops from tubo-tympanic recess

22

23

24

25 Middle Ear

26 Tympanic membrane Pearly white semi-translucent membrane Obliquely placed at 55 0 to floor 2 parts: pars tensa and pars flaccida 3 layers of pars tensa: outer epithelial, middle fibrous & inner mucosal Fibrous layer disorganized in pars flaccida Annulus deficient superiorly as notch of Rivinus

27

28

29

30 Otoscopic view

31

32 1. Epitympanum: Bounded laterally by scutum + pars flaccida & medially by bone above tympanic part of facial nerve 2. Mesotympanum: Middle ear cavity lying opposite pars tensa & bony tympanic annulus 3. Hypotympanum: Middle ear cavity below level of bony tympanic annulus 4. Posterior tympanum: Middle ear cavity behind bony tympanic annulus 5. Anterior tympanum or Pro-tympanum: Middle ear cavity in front of bony tympanic annulus

33

34 Walls of middle ear Roof: Tegmen tympani, middle cranial fossa Floor: Jugular bulb, carotid artery Anterior: Tensor tympani, ET orifice, carotid artery Posterior: Aditus, fossa incudis, pyramidal eminence, facial recess, sinus tympani Lateral: Tympanic membrane, scutum Medial: Promontory, oval window, round window, lateral SCC, facial nerve (tympanic part)

35

36

37

38 Lateral wall Membranous: a. Tympanic membrane Bony a. Lateral attic wall above pars flaccida (Scutum) b. Lateral wall of hypotympanum

39

40

41

42

43

44 Posterior wall Aditus ad antrum Fossa incudis 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

45

46

47

48

49

50 Boundaries: –Superior: Ponticulus –Inferior: Subiculum –Lateral: Mastoid Segment of Facial Nerve –Medial: Posterior semicircular canal It evades direct surgical visualization during surgery. Site for cholesteatoma recurrence Sinus Tympani

51

52 Anterior wall Chorda tympani nerve exits via canal of Huguier Canal for tensor tympani on top Eustachian tube opening below Internal carotid artery is related inferiorly

53

54

55

56 Medial wall Lateral semicircular canal Tympanic part of bony facial nerve canal Processus cochleariformis Promontory: formed by basal turn of cochlea Oval window Round window

57

58

59

60 Contents of middle ear Air 3 ossicles: malleus, incus and stapes 2 muscles: tensor tympani & stapedius 2 nerves: chorda tympani & tympanic plexus Mucosal folds & ligaments Blood vessels

61

62

63

64

65

66

67

68 Eustachian Tube

69 Anatomy 36 mm long in adults Directed anteriorly, inferiorly & medially from anterior wall of M.E., forming angle of 45 0 with horizontal & sagittal planes Enters naso-pharynx 1.25 cm behind posterior end of inferior turbinate

70

71

72

73 Parts Lateral 1/3 is bony Medial 2/3 is fibro- cartilaginous. Junction b/w 2 parts is isthmus, narrowest part of Eustachian Tube.

74 Anatomy of medial 2/3rd Cartilage plate lies postero-medially & consists of medial + lateral laminae separated by elastin hinge. Fibrous tissue + Ostmann’s fat pad lie antero-laterally.

75 Adult vs. Child (< 7 yr) ADULTINFANT Length36 mm18 mm Angle with horizontal LumenNarrowerWider Angulation at isthmusPresentAbsent CartilageRigidFlaccid Elastic recoilEffectiveIneffective Ostmann’s fatMoreLess

76 Adult vs. Child (< 7 yr)

77 Functions 1. Ventilation & maintenance of atmospheric pressure in middle ear for normal hearing 2. Drainage of middle ear secretions into nasopharynx by muco-ciliary clearance, pumping action of Eustachian tube & presence of intra-luminal surface tension

78 Functions 3. Protection of middle ear from: –Ascending nasopharyngeal secretions due to narrow isthmus & angulation between 2 parts of E.T. at isthmus –Pressure fluctuations –Loud sound coming through pharynx

79

80 Inner Ear

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99

100

101

102

103 Cochlear Hair Cells

104 Inner Hair CellsOuter Hair Cells ,000 Single rowThree or four rows Flask-shapedCylindrical Primarily afferentPrimarily efferent Transmit auditory stimuliModulate inner hair cell Resistant to damageVulnerable to damage

105

106

107

108 Vestibular Hair Cells

109

110

111

112

113

114

115 Temporal Bone

116

117

118 MacEwen’s Triangle Superior: supramastoid crest Anterior: postero-superior margin of bony external auditory canal opening Posterior: tangent drawn to mid-point of posterior wall of external auditory canal Contains spine of Henle Mastoid antrum lies mm deep to triangle

119

120

121

122 Trautmann’s triangle Boundaries Superiorly: superior petrosal sinus Posteriorly: sigmoid sinus Anteriorly: solid angle (semi-circular canals) Pathway to posterior cranial fossa from mastoid cavity & vice versa

123 Mastoid cells Central group Accessory group  Mastoid antrum  Squamous  Peri-antral  Occipital Peripheral group  Styloid  Dural  Peri-tubal  Sino-dural  Zygomatic  Peri-sinus  Petrous apex  Tip  Retro-facial

124

125

126

127 Facial Nerve

128

129

130

131

132

133

134

135

136 Thank You


Download ppt "Anatomy of Ear & Mastoid Dr. Vishal Sharma. Embryology."

Similar presentations


Ads by Google