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

What are the three areas of the ear?

A

Outer ear

Middle ear

Inner ear

2
Q

What comprises the outer ear?

A

Auricle and external auditory meatus

3
Q

What are the borders of the middle ear?

A

Between tympanic membrane and petrous part of the temporal bone

4
Q

What is the function of the outer ear?

A

To collect sound and localise sounds from different positions in space

5
Q

What are the major features of the auricle?

A

Ear canal/EAM

Tragus - hair

6
Q

What is the function of the external auditory meatus?

A

To transmit air towards the tympanic membrane

7
Q

Describe the structure of the external auditory meatus?

A

Lateral 1/3 cartilagenous, medial 2/3 bony

Lined by hair skin and cerumen glands

8
Q

What is the function of cerumen glands?

A

Produce waxy substance that prevents maceration of skin with water

9
Q

Describe the innervation of the external auditory meatus?

Why is this important?

A

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
Q

Describe the strucutre of the tympanic membrane?

A

Concave externally, convex internally

Attached to ossicles

Flaccid area

11
Q

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

When might this change?

A

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

12
Q

What is the function of the tympanic membrane?

A

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

13
Q

Describe the two cavities in the inner ear?

A

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

Tympanic cavity proper: directly medial to tympanic membrane

14
Q

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

A

Passage for infection

15
Q

What is the function of the auditory tube?

A

Connects middle ear to nasopharynx

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

16
Q

Describe the arrangement of the ossicles?

A

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

Lateral to medial: malleus, incus, stapes

17
Q

How do the ossicles transmit sound through the middle ear?

A

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

18
Q

Describe tha major features of each of the three ossicles?

A

ALL: synovial joints

Malleus: handle, head

Incus: body, lenticular process

Stapes: head, base

19
Q

Which two muscles are associated with the ossicles?

What are their functions and innervation?

A

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

20
Q

What is the chorda tympani?

What is its function?

A

Branch of facial nerve that travels through middle ear

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

21
Q

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

A

Promontory

Round window

Oval window

22
Q

What is the promontory?

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

A

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

23
Q

What are the oval and round windows?

A

Oval window: opening into inner ear

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

24
Q

Which arterial structure lies close to the ear?

A

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

25
Q

Which structure lies over the oval window?

A

Stapes

26
Q

Describe the pathway of the facial nerve around the ear?

A

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

27
Q

What are the major strucutres of the inner ear?

A

Cochlea

Semicircular canals

28
Q

Describe the structure of the cochlea and the semicircular canals?

A

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

29
Q

What is the function of the bony and membranous labyrinths?

A

Bony: transmits mechanical energy of vibration

Membranous: contains sensory receptors for hearing and balance

30
Q

Where are the sensory receptors for hearing and balance located?

A

Membranous labyrinth

31
Q

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

A

Vestibule

32
Q

Where are the sensory receptors for hearing located?

A

In cochlear duct of membranous labyrinth

33
Q

What are the componenets of the vestibule?

A

Utricle and saccule

34
Q

What is the function of the utricle and saccule?

A

Contain sensory receptors for static equilibrium

35
Q

What is the ampulla?

What is its function?

A

Swelling at the base of each semicircular canal

Contains sensory receptors for dynamic equilibrium

36
Q

Describe the orientation of the semicircular ducts?

A

3: anterior, horizontal and posterior

Anterior and posterior lie at right angles to each other

37
Q

Where are high and low frequency sounds detected?

A

High frequency: base of cochlea

Low frequency: apex of cochlea