anatomy and histology of the ear Flashcards

1
Q

what are the symptoms associated with menieres disease?

A

an inner ear disorder with symptoms that include vertigo, tinnitus, hearing loss and the sensation of ear fullness.)

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2
Q

what structures form the external ear

A

auricle, tympanic membrane, and external acoustic meatus

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3
Q

what is the blood supply of the auricle?

A

posterior auricular and superficial temporal vessels

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4
Q

what is the innervation of the auricle?

A

greater auricular nerve (cervical plexus) and auriculotemporal nerve (V3)

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5
Q

what composes the auricle?

A

concha- deep depression found in auricle
helix (outer rim)
antihelix (inner rim)
tragus (protrusion overlapping external acoustic meatus) and antitragus
lobule (contains non cartilagenous CT) everything else is elastic CT

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6
Q

what kind of glands are found within the external acoustic meatus?

A

ceraminous (wax) and sebaceous glands are found within the integument with cartilage found beneath to support the outer portion of the canal

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7
Q

what type of epithelia composes the outside layer of the tympanic membrane?

A

stratified squamous epithelium

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8
Q

what epithelia lines the inside layer of the tympanic membrane?

A

simple cuboidal epithelium

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9
Q

what is the tip of the tympanic membrane called and where is it pointed to

A

umbo; pointed towards the external acoustic meatus

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10
Q

where does the tympanic membrane transmit its movement (sound)?

A

transmits movement by sound to the ossicles

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11
Q

what is the innervation of the tympanic membrane?

A

A) external surface by auriculotemporal nerve

B) inner surface by small branch of CN V3 and by small auricular branch of vagus nerve

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12
Q

what antibiotic should you avoid when treating a perforated tympanic membrane?

A

gentamycin

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13
Q

what structures are found within the middle ear (tympanic cavity)?

A

within the tympanic cavity lies the auditory ossicles: stapes, incus, and malleus; round and oval window; pharyngotympanic tube (eustachian tube)

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14
Q

what is the location for the external ear?

A

dense petrous portion of the temporal bone

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15
Q

what is the location for the middle ear?

A

petrous portion of temporal bone

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16
Q

what are the two parts of the middle ear?

A

tympanic cavity proper and epitympanic recess

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17
Q

what are the walls of the middle ear?

A

tegmental wall (epitympanic recess- roof); jugular wall (floor); membranous wall (lateral); labyrinthine wall (medial); mastoid wall (posterior); carotid wall (anterior)- near opening of pharyngotympanic tube and canal for tensor tympani

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18
Q

describe the eustachian tube (pharyngotympanic tube)

A

connects tympanic cavity with nasopharynx- functions to equalize pressures; posterolateral part is bone, rest is elastic cartilage

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19
Q

what structures is the eustachian tube open to?

A

levator veli palatine, tensor veli palatine and salpingopharyngeus muscles

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20
Q

what is the course for auditory ausicles?

A

from tympanic membrane to oval window of cochlea

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21
Q

what does the base/ footplate of the stapes (stirrup) attach to?

A

the oval window

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22
Q

what muscles are associated with the ossicles within the middle ear?

A

tensor tympani muscle (V), stapedius muscle (VII),

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23
Q

what is the function of the tensor tympani muscle within the middle ear?

A

inserts on handle of malleolus and pulls on handle to tense tympanic membrane and reduce amplitude.

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24
Q

what is the function of the stapedius muscle within the middle ear?

A

inserts on the stapes and pulls the stapes posteriorly tightening annular ligament attaching it to window oval window; reduces oscillatory range and prevents excessive movement of the stapes

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25
Q

define otitis media

A

ear-ache with possible fluid or pus in the middle ear due to inflammation or infection; tympanic membrane appears red and bulged; fluid may be visible through membrane; untreated can impair hearing and scarring of auditory ossicles

26
Q

define mastoiditis

A

Infection of mastoid cells; can spread into cranial fossa via petrosquamous cranial suture. Treated with antibiotics

27
Q

what structures compose the inner ear?

A

bony labyrinth (semicircular canals, vestibule, cochlea); membranous labyrinth (vestibular division: semicircular DUCTS, utricle, saccule), vestibular and cochlear aqueducts, endolymphatic sac found at the end of the vestibular aqueduct; perilymphatic space, endolymphatic space, hair cells, cochlea, stria vascularis, organ of corti, scala vestibuli, scala tympani, osseous spiral lamina

28
Q

where is the endolymphatic duct located within the inner ear?

A

within the vestibular aqueduct

29
Q

define vestibule

A

space containing saccule and utricle within inner ear

30
Q

describe the membranous labyrinth

A

lies within bony labyrinth (cavities within bone) and consists of small sacs and tubules forming continuous spaces enclosed by an epithelium

31
Q

describe the vestibular division within the membranous labyrinth (inner ear)

A

contains semicircular ducts, utricle and saccule for balance and orientation

32
Q

what is the function of the cochlea

A

sound

33
Q

describe the sensory cells found within the membranous labyrinth (inner ear)

A

sensory cells are found within 6 regions (3 cristae ampullari, 2 maculae (detect linear acceleration in 3 dimensions), one organ of corti); hair cells and support cells; mechanosensory cells - convert mechanical energy into electrical energy transmitted via CN VIII (vestibulocochlear) to brain.

34
Q

describe perilymphatic space within the inner ear

A

lies between bony and membranous labyrinths; composition similar to CSF; drains via perilymphatic duct (cochlear aqueduct) into subarachnoid space

35
Q

describe endolymphatic space

A

within membranous labyrinth; high in K+ but low in Na+; originates from stria vascularis; drains via endolymphatic duct into venous sinuses of dura mater

36
Q

describe hair cells

A

sensory cells found arranges in rows that have an array of stereocilia that increase in height along a particular direction

37
Q

describe cilia within vestibular system (inner ear)

A

vestibular system contains one true cilia (kinocilium) located behind tallest stereo cilia

38
Q

describe cilia within auditory system

A

cilia structure is lost but retain kinocilium’s basal body

39
Q

how is the movement of stereocilia perceived differently?

A

depends on if the stereocilia move toward or away from kinocilia or tallest cilia; if deflected toward tallest stereocilia, K+ channels open; channels close if movement is in opposite direction

40
Q

describe stereocilia

A

stiff and contain mechanoelectrically-gated ion channels

41
Q

describe the innervation of hair cells

A

innervated by both efferent (modulate sensitivity) and afferent nerves - target of ototoxicity effects by some antibiotics (gentomycin)

42
Q

what are the three compartments of the cochlear duct (soft tissue)?

A

scala media (cochlear duct)- middle compartment contains endolymph; scala vestibuli - contains perilymph and fluid is moved by stapes at oval window; continuous with scala tympani; scala tympani - connected to round window

43
Q

describe the osseous spiral lamina

A

part of the cochlea- inner spiraling bony shelf serving as support for tectorial membrane and spiral ganglia

44
Q

what composes the scala media (middle compartment of cochlea containing endolymph)?

A

stria vascularis - lateral wall of scala media; source of endolymph; organ of corti- on floor of scala media resting on basilar membrane

45
Q

what is the source of endolymph

A

stria vascularis within the scala media of the cochlear duct (inner ear)

46
Q

describe the components of the organ of corti

A

floor of scala media of cochlear duct; composed of hair cells (sensory), inner and outer pharyngeal cells (support for hair cells) and pillar cells (support between basilar membrane and tympanic lip)

47
Q

describe the structure and mechanism of sound of the organ of corti

A

3 rows of outer hair cells, single row of inner hair cells; hair cell stereocilia are embedded in overlying tectorial membrane extending from the spiral lamina; basilar membrane vibrates with sound causing deflection of stereocilia attached to tectorial membrane, opening K+ channels in hair cells; bipolar neuron cell bodies located in spiral ganglion transmit the signal to the CNS via the vestibulocochlear n (CN VIII)

48
Q

describe the path of sound waves within the cochlea>

A

high frequencies detected near the base of the cochlea while low frequency closer to the tip of the duct. Amplitude is dependent on degree of displacement.

49
Q

what are the steps to producing sound within the cochlea?

A
  1. stapes moves oval window causing a fluid pressure wave formation in perilymph
  2. wave distorts vestibular membrane causing a pressure wave within endolymph of the scala media
  3. this displaces basilar membrane and distorts stereocilia of hair cells
  4. pressure in perilymph is transferred to scala tympani and exits via round window
50
Q

describe conductive hearing loss

A

effects outer and middle ear; fluid build-up in middle ear, otitis, excessive ear wax, otosclerosis (stiffening of ear bone joints)

51
Q

describe sensorineural hearing loss

A

reduction in sound level and or fidelity due to damage to inner ear or auditory nerve; affects hearing at different frequencies and intensities - age related, noise induced; central hearing loss- problem with CNS

52
Q

describe the semicircular canals and ampulla of the middle ear

A

3 canals in 3 different axes; endolymph filled and connected to utricle; ends of canals have an ampulla with gelatinous like cap called a cupula. Sensory hair cells are attached to cupula.

53
Q

describe the function of the cupula

A

sensory hair cells are attached to the cupula (gelatinous cap at the end of the ampulla of the semicircular canals of the inner ear);

cupula is displaced by fluid motion within the canals - serve as sensors of rotational velocity.

54
Q

describe the utricle and saccule (inner ear)

A

each contain a macula comprised of:

a) a cluster of hair cells with stereocilia with overlying gelatinous material called otolithic membrane;
b) otolithic membrane covered with calcium carbonate/protein crystals called otoconia.

55
Q

what is the function of the utricle and saccule within the inner ear?

A

serve as sensors for gravity and linear acceleration

56
Q

what is the physiology associated with meniere’s syndrome (disease assoc. with membrane labyrinth)

A

associated with increased endolymph volume leading to abnormal signaling; cause is unclear

57
Q

what are the possible treatments for meniere’s syndrome (membrane labyrinth assoc. disease)

A

mild cases are treated with medication; severe cases may require surgical ablation of parts of labyrinthine system but there are risks of permanent hearing loss.

58
Q

define viral labyrinthitis

A

dizziness, vertigo, tinnitus, some muffled hearing; usually resolves within a week

59
Q

what are the three sensory systems

A

audition, rotational velocity, gravity/linear acceleration

60
Q

what are the three nerves in the acoustic meatus?

A

vestibular (VIII), acoustic nerve, facial nerve (VII)

61
Q

scala vestibuli

A

contains perilymph and fluid is moved by stapes at the oval window; continuous with scala tympani also filled with perilymph connected to round window

62
Q

scala tympani

A

filled with perilymph connected to round window