Ear and Auditory Canal (ENT 1) Flashcards Preview

MD1 Neuroscience > Ear and Auditory Canal (ENT 1) > Flashcards

Flashcards in Ear and Auditory Canal (ENT 1) Deck (103):
1

Where does the outer ear end?

At tympanic membrane

2

Where is the inner ear?

Embedded in petrous part of temporal bone

3

What structure is for hearing?

Cochlea

4

What structure is for balance and equilibrium?

Vestibule

5

What structures make up the outer ear?

Auricle
External acoustic meatus

6

Where is the auricle?

Outside part of ear

7

What is the function of the auricle?

Collect sound

8

What is the auricle made of?

Cartilage

9

What is the tragus?

Little flap of skin over external auditory meatus

10

What is the external auditory meatus made of?

Lateral 1/3 cartilagenous
Medial 2/3 bony - embedded in temporal bone

11

What is the innervation of the external auditory meatus?

Posterior and inferior surface innervated by vagus
Anterior and superior surface innervated by auriculotmporal = branch of V3

12

Where can pain be referred to from the anterior and superior part of the external auditory meatus?

Teeth because of V3 innervation of both

13

What is the external auditory meatus lined by?

Hairy skin embedded with cerouminous glands

14

What do cerouminous glands produce?

Cerumen = ear wax

15

What is the function of cerumen?

Protect skin from water

16

Where does sound run from the auricle?

Into external auditory meatus > tympanic membrane

17

Where is the tympanic membrane?

Forms almost complete seal of external auditory meatus into middle ear

18

What is the bump on the tympanic membrane formed by?

Handle of malleus

19

Why does shining a light on the tympanic membrane produce a cone of reflected light on it?

Because it's concave

20

Where is the cone of reflected light on the tympanic membrane?

In antero-inferior quadrant

21

What is the clinical significance of the position of the cone of light on the tympanic membrane?

Increased pressure in middle ear pushes membrane out a little bit > changes position of cone of light

22

What is the nerve supply to the mucosa of the middle ear?

Mostly from glossopharyngeal nerve

23

Where can pain from the middle ear be referred to?

Other areas supplied by the glossopharyngeal nerve, especially tonsils

24

What is the transmission of sound through the middle ear?

Sound waves make tympanic membrane vibrate > transmitted to middle ear

25

What is the structure of the middle ear?

Largely a space in petrous part of temporal bone
Made of 2 compartments

26

What are the two compartments of the middle ear?

Epitympanic recess
Tympanic cavity proper

27

Where is the tympanic cavity proper?

Medial to tympanic membrane

28

Where is the epitympanic recess?

Above medial tympanic membrane

29

What does the epitympanic recess communicated with?

Mastoid sinuses

30

What is the clinical significance of the communication between the epitympanic recess and mastoid sinuses?

Inflammation in epitympanic recess can move to mastoid air cells in mastoid process > pain and further infection

31

How are infections of the mastoid air cells cleared?

Antibiotics

32

How does the middle ear communicate with the nasal cavity?

Auditory tube

33

Where is the auditory tube?

Projects from anterior and inferior wall of middle ear
To nasopharynx

34

What is the function of the auditory tube?

Allows for equalisation of pressure in middle ear and atmosphere

35

What happens if the middle ear cannot equalise with the atmosphere?

Creates movement in tympanic membrane
If severe, can damage it

36

How can you get a middle ear infection?

Bacteria from nasal cavity moves up auditory tube to middle ear
Causes pain

37

What is the clinical significance of the position of the auditory tube?

In adults, auditory tube projects downwards significantly > difficult for bacteria to move up tube, and allows infections to drain down
In infants, tube far more horizontal > easier for bacteria to move to middle ear

38

By when do chronic middle ear infections tend to resolve in children?

Ages 6-7

39

How many ossicles are there?

3

40

Where are the ossicles?

In middle ear

41

What do the ossicles articulate with?

Each other
Tympanic membrane laterally
Oval window medially

42

What is the function of the ossicles?

Transmit sound from middle ear to inner ear

43

Which ossicle is most lateral?

Malleus

44

What does the malleus articulate with?

Handle articulates with tympanic membrane laterally
Head articulates with incus

45

Which ossicle is in the middle?

Incus

46

What does the incus articulate with?

Malleus
Head of stapes

47

Which ossicle is the most medial?

Stapes

48

What does the stapes articulate with?

Head with incus
Oval shaped base sits directly over oval window

49

What kind of joints are the articulations between the ossicles?

Synovial

50

What anchors some of the muscles to the walls of the middle ear?

Small muscles

51

Which muscle articulates with malleus?

Tensor tympani anteriorly

52

Which muscle articulates with stapes?

Stapedius posteriorly

53

Which nerve innervates tensor tympani?

Trigeminal nerve

54

Which nerve innervates stapedius?

CN VII

55

What is the role of tensor tympani and stapedius?

Dampen loud sounds to protect inner ear

56

Is the contraction of tensor tympani and stapedius voluntary?

No, reflexive contraction

57

How do tensor tympani and stapedius dampen sound?

Muscles pull on ossicles to dampen vibration

58

What is the clinical significance of damage to the facial nerve in relation to stapedius?

Reflexive mechanism won't work
People more sensitive to sound because can't regulate dampening of energy
Eg: in Bell's palsy people more sensitive to large sounds

59

What is the landmark for the oval and round windows?

Promotnary formed by basal turn of cochlea

60

Where is the oval window?

Superior and posterior

61

Where is the round window?

Inferior and posterior

62

Which window communicates with the inner ear?

Both oval and round windows

63

Which nerve goes through the middle ear?

Chorda tympani

64

What is the function of chorda tympani?

Taste to anterior 2/3 of tongue
Parasympathetic innervation to some salivary glands

65

Which cranial nerve is the chorda tympani a branch of?

Facial nerve

66

Where does chorda tympani enter and exit the middle ear?

Enters through posterior wall
Exits through anterior wall

67

With which nerve does chorda tympani hitchhike to the mouth?

Inguinal nerve - branch of CN V

68

From which wall does the auditory tube project?

Projects from anterior wall, anteriorly and inferiorly

69

What is the route of the facial nerve through the middle ear?

Enters through internal auditory meatus
Arches over top of middle ear
Moves posteriorly to exit skull
Exits through stylomastoid foramen

70

Which artery is very close to the facial nerve?

Internal carotid

71

What is the bony labyrinth?

Oval window opens into series of spaces embedded in petrous part of temporal bone

72

What is the fluid in the bony labyrinth?

Perilymph

73

What is suspended inside the bony labyrinth?

Membranous labyrinth

74

What is the membranous labyrinth made of?

Single tube of membrane

75

What is the fluid in the membranous labyrinth?

Endolymph

76

What is the shape of the cochlea?

Snail shell

77

Where are the sensory receptors for hearing?

In cochlea

78

How many semicircular canals are there?

3

79

Where is the vestibule?

Between semicircular canals and cochlea

80

Into which structure do the oval and round windows open?

Vestibule

81

How does sound energy enter and exit the inner ear?

Enters through oval window
Exits through round window

82

Where are the utricle and saccule?

In vestibule
Utricle superior
Saccule inferior

83

What is the function of the untricle and saccule?

Provide info about static equilibrium
Also provide a little info about dynamic equilibrium

84

What is knowing head position important for?

Balance
Many reflexes around this

85

What is static equilibrium?

Head position

86

What is dynamic equilibrium?

Head movement

87

What nerve carries sound information from the cochlear duct to the brain?

Cochlear nerve

88

What nerve carries equilibrium information from the ampulla, utricle, and saccule to the brain?

Vestibular nerve?

89

What nerves form CN VIII?

Cochlear nerve
Vestibular nerve

90

What are the three semicircular ducts?

Anterior
Posterior
Horizontal

91

Why is the orientation of the semicircular ducts important?

For equilibrium

92

What is the orientation of the anterior semicircular duct?

Vertical
Projects anterolaterally

93

What is the orientation of the posterior semicircular duct?

Vertical
Projects posterolaterally

94

What is the orientation of the horizontal semicircular duct?

Horizontal

95

What does the ampulla detect?

Dynamic equilibrium

96

In which direction does the cochlear duct project?

Anteromedially along line of petrous part of temporal bone

97

What is the frequency and amplitude of sound transmitted by the tympanic membrane as compared to that in air?

Same frequency
Relative amplitude

98

What is the frequency and amplitude of sound transmitted by perilymph as compared to that in air?

Same frequency
Relative amplitude

99

What does perilymph transmit sound energy to?

Membranous labyrinth and sensory receptors

100

Where are the sensory receptors that respond best to high frequencies?

At base of cochlea

101

Where are the sensory receptors that respond best to low frequencies?

At apex of cochlea

102

What is coded by the amplitude of a sound wave?

Loudness

103

How do equilibrium sensory receptors work?

Endolymph heavy so with head movements it lags behind
Moves across ampulla to stimulate receptors
Brain decodes vector representation of head movement depending on relative excitation of receptors

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