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Flashcards in Ear and auditory tube Deck (37):
1

What are the three areas of the ear?

Outer ear

Middle ear

Inner ear

2

What comprises the outer ear?

Auricle and external auditory meatus

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3

What are the borders of the middle ear?

Between tympanic membrane and petrous part of the temporal bone

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4

What is the function of the outer ear?

To collect sound and localise sounds from different positions in space 

5

What are the major features of the auricle?

Ear canal/EAM

Tragus - hair

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6

What is the function of the external auditory meatus?

To transmit air towards the tympanic membrane

7

Describe the structure of the external auditory meatus?

Lateral 1/3 cartilagenous, medial 2/3 bony 

Lined by hair skin and cerumen glands 

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8

What is the function of cerumen glands?

Produce waxy substance that prevents maceration of skin with water 

9

Describe the innervation of the external auditory meatus?

Why is this important?

Vagus (posteroinferior)

Auriculotemporal nerve (V3 branch - anterosuperior and external surface of tympanic membrane)

Important because EAM can refer pain to opther branches of V3 (eg. teeth)

10

Describe the strucutre of the tympanic membrane?

Concave externally, convex internally

Attached to ossicles

Flaccid area 

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11

Describe the cone of light that should be seen when looking into the ear with an oroscope?

When might this change?

Cone of light in antero-inferior quadrant

When pressure builds up in middle ear, concavity of tympanic membrane will change and alter the position of the light 

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12

What is the function of the tympanic membrane?

Vibrates with same frequency and amplitude relative to sound waves > transmits energy into middle ear and beyond 

13

Describe the two cavities in the inner ear?

Epitympanic recess: space above the tympanic membrane, communicates posteriroyl with spaces in mastoid bone 

Tympanic cavity proper: directly medial to tympanic membrane 

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14

What is the significance of the communication between the epitympanic recess and the mastoid air cells?

Passage for infection 

15

What is the function of the auditory tube?

Connects middle ear to nasopharynx

Allows communication between middle ear and atmosphere, therefore allowing equalisation of pressure to occur

16

Describe the arrangement of the ossicles?

Attached laterally to tympanic membrane, attached medially to hole in petrous part of the temporal bone

Lateral to medial: malleus, incus, stapes 

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17

How do the ossicles transmit sound through the middle ear?

Tympanic membrane vibrates > ossicles vibrate with same frequency and amplitude relative to that sound > sound waves transmitted through to inner ear

18

Describe tha major features of each of the three ossicles?

ALL: synovial joints

Malleus: handle, head

Incus: body, lenticular process

Stapes: head, base

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19

Which two muscles are associated with the ossicles?

What are their functions and innervation?

Stapedius: attaches to stapes, innervated by CN VII

Tensor tympani: attaches to malleus, innervated by CN V

Both contract to dampen the amplitude of vibration of ossicles for loud sounds  

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20

What is the chorda tympani?

What is its function?

Branch of facial nerve that travels through middle ear

Carries PS nerve fibres to salivary glands and brings back info about taste from tongue

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21

What are the major features of the medial wall of the middle ear?

Promontory

Round window

Oval window 

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22

What is the promontory?

Where do the oval and round window lie relative to it?

Basal turn of cochlea that impresses on the medial wall of the middle ear

Oval window is posterior and above

Round window is posterior and below 

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23

What are the oval and round windows?

Oval window: opening into inner ear

Round window: opening from inner ear back out into middle ear, which allows for pressure release 

24

Which arterial structure lies close to the ear?

Internal carotid artery lies close to middle ear (runs straight underneath it)

25

Which structure lies over the oval window?

Stapes 

26

Describe the pathway of the facial nerve around the ear?

Enters petrous part of temporal bone through internal auditory meatus > travels in facial canal > emerges in stylomastoid foramen 

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27

What are the major strucutres of the inner ear?

Cochlea

Semicircular canals

28

Describe the structure of the cochlea and the semicircular canals?

Bony labyrinth: space in petrous part of temporal bone, filled with perilymph

Membranous labyrinth: closed sac that is suspended in perilymph of bony labyrinth, filled with endolymph 

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29

What is the function of the bony and membranous labyrinths?

Bony: transmits mechanical energy of vibration 

Membranous: contains sensory receptors for hearing and balance

30

Where are the sensory receptors for hearing and balance located?

Membranous labyrinth

31

What is the connection between the cochlea and the semicircular canals called?

Vestibule 

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32

Where are the sensory receptors for hearing located?

In cochlear duct of membranous labyrinth 

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33

What are the componenets of the vestibule?

Utricle and saccule

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34

What is the function of the utricle and saccule?

Contain sensory receptors for static equilibrium 

35

What is the ampulla?

What is its function?

Swelling at the base of each semicircular canal

Contains sensory receptors for dynamic equilibrium 

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36

Describe the orientation of the semicircular ducts?

3: anterior, horizontal and posterior 

Anterior and posterior lie at right angles to each other 

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37

Where are high and low frequency sounds detected?

High frequency: base of cochlea

Low frequency: apex of cochlea

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