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Module 8 > Anatomy of Ear > Flashcards

Anatomy of Ear Flashcards

1
Q

what is the functions of the ear

A
  1. hearing + balance –> vestibulocochlear organ
  2. hearing –> transformation of mechanical sound waves into nerve impulses
  3. balance –> changes in fluid levels within inner ear
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2
Q

what are the two parts of the external ear

A
  1. auricle or pinna (“ear”)
  2. external acoustic meatus (canal connecting base of auricle to tympanic membrane)
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3
Q

what is the shape of the auricle or pinna

A

funnel shaped –> wide distally and narrows to connection with external acoustic meatus

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4
Q

what is the shape of the auricle determined by

A

auricular cartilage –> variable stiffness

rolls to form cone shape

also annular cartilage at base of auricular cartilage (anchors auricle to skull)

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5
Q

name the structures of the external ear

A
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6
Q

where do the vessels of the external ear run

A

run on convex (outer) surface

branch from caudal auricular artery (from external carotid)

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7
Q

where does the external ear canal run

A

from “closure” of auricular cartilage to ear drum

vertical and horizontal parts (hockey stick shape)

curves ventrally then rostromedially (difficult to examine with otoscope)

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8
Q

what is the external ear canal lined with

A

skin

sebaceous and tubular ceruminous glands (secrete wax)

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9
Q

name the structures shown of the external ear canal

A
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10
Q

what are the 4 components of the middle ear

A
  1. tympanic cavity (contains but often referred to as tympanic bulla)
  2. tympanic membrane
  3. auditory ossicles
  4. auditory tube (aka eustacian tube)
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11
Q

where does the tympanic cavity lie

A

within temporal bone (lateral to petrous temporal bone)

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12
Q

what is the tympanic cavity

A

air filled

thin mucus membrane lining (drain secretions so it doesn’t fill with fluid)

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13
Q

how can the tympanic cavity be divided

A

dorsal and ventral parts

dorsal - epitympanic recess

ventral = tympanic bulla

two windows dorsomedially –> dorsal = vestibular and ventral = cochlear

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14
Q

name the structures of the tympanic cavity

A
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15
Q

what does the tympanic membrane divide

A

external acoustic meatus from middle ear

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16
Q

what are the surfaces of the tympanic membrane called

A

epidermal (outer) and mucosal (inner) covering

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17
Q

what does the tympanic membrane attach to

A

fibrous attatchment to typmanic ring of temporal bone

medial surface attachted to ossicles

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18
Q

what is the order of the auditory ossicles from lateral to medial

A

malleus (hammer)

incus (anvil)

stapes (stirrup)

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19
Q

what is attached to the eardrum

A

handle/manubrium of malleus

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20
Q

how do articulations of the auditory ossicles occur

A

malleus-incus-stapes

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21
Q

where does the stapes insert into

A

vestibular window

22
Q

what do ligaments attach the ossicles to

A

epitympanic recess

23
Q

what are the auditory ossicle muscles

A

tensor tympani stapedius

tense eardrum and ossicle chain –> protecting

reduces vibrations when loud noises (by contracting)

24
Q

what are the structures of the auditory ossicles

A
25
Q

how does hearing work

A
  1. sound causes vibration of tympanic membrane
  2. motion transmitted through ossicle chain
  3. causes vibration in inner ear fluid at vestibular window
  4. transmission via walls of tympanic cavity and cochlear window
26
Q

where does the auditory tube connect

A

tympanic cavity to nasopharynx

–> openings in lateral wall of nasopharynx

runs in cartilage trough –> out-pouching in horses = guttural pouch

27
Q

what state is the auditory tube normally in and what is its function

A

usually collapsed

when open allows equalization of pressure on either side of tympanic membrane

allows drainage of material from tympanic cavity –> swallowing opens canal and allows drainage of secretions

if doesnt open –> fluid buildup in inner ear

28
Q

what structure is this

A

auditory tube

29
Q

what is the function of the inner ear

A
  1. hearing –> transformation of mechanical stimuli (sound) into nerve impulses
  2. organs of balance
30
Q

what is the inner ear enclosed in

A

petrous temporal bone –> osseous labyrinth

contains perilymph around membranous labyrinth

31
Q

what are the system of membranous ducts and cavities in the inner ear called and what do they contain

A

membranous labyrinth

contains endolymph

32
Q

what are the central cavities of the inner ear called

A
  1. utriculus
  2. sacculus
33
Q

what are the 3 ducts in the inner ear

A

3 semicircular ducts from

  1. utriculus - balance
  2. spiral cochlear duct fom
  3. sacculus - hearing
34
Q

what stimulates sensory hairs in the inner ear

A

movement of endolymph stimulates sensory hairs on receptor cells in wall of labyrinth –> nerve signal generated

35
Q

what are the structures of the inner ear

A
36
Q

what do the utriculus and sacculus contain and what are their functions

A

further receptors

  1. maculae (otolith organs)
  2. crystals (statoconia, otoliths) adhere to sensory hairs

determine position of head relative to gravity

37
Q

where are the semicircular ducts orientated

A

at right angles

anterior, posterior and lateral

ampullae at one insertion into utriculus

38
Q

what is the function of the semicircular ducts

A

fluid moves with head movement

stimulates sensory hairs and cells on the cristae ampullares (barriers present in ampullae)

fluid moves slower than head because of intera

39
Q

what is this structure

A
40
Q

what is nystagmus

A

flicking movement of eyes in response to movement of fluid in semicircular canals

seen after stopping rotation

dizziness

may be seen with brain disorders

41
Q

what does the osseous labyrinth contain

A
  1. central chamber –> vestibule (contains ultriculus and sacculus)
  2. semicircular canals –> contains semicircular ducts
  3. cochlea –> contains cochlear duct (spiral), central osseous pyramid (modiolus) with canal running around and projecting spiral lamina (thread of screw)
42
Q

what is the cochlea

A

membrane from spiral lamina divides into 3 channels

wall between cochlear duct and scala tympani

43
Q

what are the 3 channels of the cochlea

A
  1. scala vestibuli
  2. cochlear duct
  3. scala tympani
44
Q

what does the wall between cochlear duct and scala tympani contain

A

neuroreceptors = spiral organ (aka organ of corti)

45
Q

how does the inner ear contribute to hearing

A
  1. vibrations at vestibular window (from stapes) and cochlear window
  2. transmitted through perilymphatic space
  3. causes vibration of basement membrane and movement of sensory cilia
  4. registered by neuroreceptors
  5. transmitted to vestibulocochlear nerve (VIII)
46
Q

what is the nerve supply to the ear

A
  1. vestibulocochlear nerve –> divides into vestibular and cochlear parts at internal acoustic meatus (vestibular - balance, and cochlear - hearing)
  2. facial nerve –> stapedius m
  3. mandibular nerve (V) –> tensor tympani m
47
Q

what is the vascular supply and venous drainage to the external ear

A

arterial supply from external carotid via caudal auricular

venous drainage to maxillary vein

48
Q

what is the vascular supply to middle and inner ear

A

arterial supply from occipital artery branching from external carotid

49
Q

what is a aural hematoma

A

hematoma under skin of pinna

swollen, painful

drain with needle

50
Q

where does the facial nerve pass through in the ear

A

through inner and middle ears

enters at internal acoustic meatus

runs dorsal to epitympanic recess –> chorda tympani criss dorsal part of tympanic membrane

–> sympathetic supply to eye passes between tympanic bulla and petrous temporal bone

51
Q

how is the ear imaged

A
  1. otoscope
  2. radiography (widely available, tympanic bullar superimposed on other skull structures)
  3. advanced imaging (CT/MRI) –> clear imaging of inner and middle ear
52
Q

what is otitis

A

inflammation or infection of ear

otitis externa (external ear)

otitis media (middle ear)

otitis interna (inner ear)

Module 8 (43 decks)

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