7. The middle ear (lecture) Flashcards

1
Q

what does the middle ear contain?

A

ossicles and an air filled cavity

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2
Q

where is the air filled cavity of the middle ear situated?

A

between the tympanic membrane and the inner ear

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3
Q

what does the air filled cavity within the middle ear contain?

A

ossicles

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4
Q

what is the function of ossicles within the middle ear?

A

AMPLIFY vibration from the tympanic membrane (external ear order) to the cochlea via the oval window (inner ear opening)
(transmitting sound from middle to inner ear)

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5
Q

what are the ossicles contained within the middle ear?

A

malleus
incus
stapes

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6
Q

where do sound waves begin transmission? to?

A

pinna and ear canal transmit sound waves to the tympanic membrane, sound waves make tympanic membrane vibrate (vibrating ossicles up to 20x)

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7
Q

which ossicle (middle ear) attaches to the tympanic membrane (external ear)?

A

malleus attaches to tympanic membrane

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8
Q

what is significant about the ossicles?

A

smallest bones of the body

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9
Q

which ossicle attaches to the inner near?

A

stapes attaches to the oval window (of cochlea)

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10
Q

What is Cochlea full of?

A

fluid

why ossicles have to vibrate far harder - to send vibrations through fluid of cochlear of inner ear

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11
Q

what is the function of the oval window of cochlea? (attached to stapes)

A

It allows fluid in the cochlea to move, which in turn ensures that hair cells of the basilar membrane will be stimulated and that audition will occur

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12
Q

what is pressure within the middle ear equalised by?

A

by the eustachian (pharyngotympanic) tube to the same as atmospheric pressure
(lateral nasopharynx - upper resp infection - otitis media, perforate TM)

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13
Q

where is the middle ear?

A

behind the tympanic membrane

air filled cavity WITHIN petrous part of temporal bone

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14
Q

what is above the 3 ossicles within the middle ear?

A

epitympanic recess

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15
Q

aside from pressure equilibration, what is another function of the eustachian (pharyngotympanic) tube?

A

ventilation and drainage of mucus from middle ear

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16
Q

what does the pharyngotympanic (eustachian) tube connect?

A

lateral nasopharynx and middle ear

17
Q

what is a common condition involving the middle ear?

A

otitis media with effusion

18
Q

what is otitis media with effusion also known as?

A

glue ear

19
Q

what is otitis media with effusion (glue ear)?

A

not an actual infeciton

build up of fluid and negative pressure in middle ear

20
Q

what can cause otitis media with effusion (glue ear)?

A

due to eustachian tube dysfunction: but CAN predispose to infection

21
Q

what does otitis media with effusion (glue ear) cause?

A

decreases mobility of tympanic membrane and ossicles - affecting hearing (quieter)

22
Q

how do you treat otitis media with effusion (glue ear) cause?

A

most resolve spontaneously in 2-3 months

some may persist and require grommets

23
Q

what is a grommet?

A

a tube surgically implanted in the eardrum to drain fluid from the middle ear

24
Q

how does the TM appear in otitis media with effusion (glue ear) upon examination with otoscope?

A

TM appears retracted and looks straw coloured (instead of pearly)

25
Q

why does TM appear retracted in otitis media with effusion (glue ear)?

A

tympanic membrane sucked in towards the eustachian tube from negative pressure within the middle ear

26
Q

why does the TM appear straw coloured in otitis media with effusion (glue ear)?

A

discolouration from fluid buildup

27
Q

how does eustachian tube equalise pressure in the middle ear?

A

every so often, the Eustachian tube opens up to allow drainage of the mucous and to equalise pressure

28
Q

why can there be a buildup of pressure within the middle ear if the eustachian tube is blocked?

A

cells within the middle cavity absorbs air, so blockage of eustachian tube causes buildup of pressure - negative pressure
(fluid builds up - not drained)

29
Q

what happens when the eustachian tube is blocked?

A

tympanic membrane and ossicles won’t vibrate as well
affects hearing
doesn’t cause pain

30
Q

what can otitis media with effusion (glue ear) predispose to?

A

infection

from stasis of fluid

31
Q

aside from otitis media with effusion, what is another common condition involving the middle ear?

A

otitis media

32
Q

what is otitis media?

A

acute middle ear infection

33
Q

which age group is more prone to otitis media?

A

more common in infants, children than in adults

34
Q

how do children with otitis media present?

A

otalgia (infants may pull or tug at the ear) - from pain within

35
Q

aside form otalgia, what other symptoms can otitis media present with?

A

other non-specific symptoms of infection e.g. temperature

36
Q

how would the TM appear during examination with otoscope?

A

red +/- bulging TM

loss of normal landmarks of TM