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Histology - Exam 4 > Sensory Systems - Ear > Flashcards

Sensory Systems - Ear Flashcards

1
Q

what is the auricle?

A

irregularly shaped internal plate of elastic cartilage

-thin skin w/ hair and sebaceous glands

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2
Q

describe lining of external auditory meatus

A

thin skin - also lines outer surface of ear drum

  • has large sebaceous glands
  • has coiled tubuloalveolar ceruminous glands
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3
Q

what is ear wax?

A

mixture of ceruminous and sebaceous secretions + desquamated meatal cells

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4
Q

tympanic cavity: what is in it and what does it connect?

A
  • houses ossicles

- connected to pharynx by eustachian tube

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5
Q

lining of tympanic cavity

A

simple squamous epithelium that changes to pseudostratified ciliated columnar near the opening to the auditory tube

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6
Q

what are the oval and round windows?

A

small, membrane-covered regions devoid of bone that separate the middle ear from the bony labyrinth of the inner ear

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7
Q

what are the three ossicles?

A

malleus, incus, stapes

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8
Q

function of the ossicles

A

transmits tympanic membrane movements to oval window

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9
Q

describe the inner ear

A

a fluid-filled membranous labyrinth within a bony labyrinth

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10
Q

endolymph vs. perilymph

A 
endolymph = fluid inside membranous labyrinth (like intracellular fluid, w/ low Na+, protein and high K+) 
perilymph = fluid outside membranous labyrinth (like ECF, but low protein)
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11
Q

what do the semicircular canals contain?

A

semicircular ducts of membranous labyrinth

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12
Q

what is contained by the vestibule?

A

contains perilymph and houses saccule and utricle (which have endolymph)

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13
Q

describe the cochlea

A

winds 2.5x around modiolus and subdivided into 3 spaces:

  • scala vestibuli (filled w/ perilymph)
  • scala tympani (filled w/ perilymph)
  • scala media (cochlear duct)
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14
Q

what is the modiolus?

A

bony core of cochlea that has blood vessels and spiral ganglion

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15
Q

what do the lateral extensions of the modiolus form?

A

osseous spiral lamina

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16
Q

what is the thickened periosteum around the cochlea?

A

spiral ligament

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17
Q

where are the saccule and utricle found?

A

inside the vestibule

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18
Q

what are the saccule and utricle and what is their lining?

A

sac-like bodies of CT lined by simple squamous epithelium that each give off a duct

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19
Q

where do the ducts of the saccule and utricle end up?

A

they join to form the endolymphatic sac

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20
Q

what do the saccule and utricle contain?

A

maculae - specialized regions that have 2 types of neuroepithelial hair cells

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21
Q

in general, what are vestibular hair cells?

A

neuroepithelial cells that have 50-100 rigid stereocilia arranged in rows + a single cilium (kinocilium)
-round, basal nucleus

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22
Q

function of the stereocilia on vestibular hair cells

A

sensory microvilli

23
Q

describe location of vestibular hair cell cilia

A

extend from apical surface of hair cells to an overlying gelatinous layer (otolithic membrane)

24
Q

describe type I hair cells

A
  • bulbar shape w/ round nucleus

- surrounded by cup-shaped afferent nerve ending

25
Q

describe type II hair cells

A
  • columnar w/ a round, basal nucleus

- contact small afferent nerve terminals w/ synaptic vesicles

26
Q

describe support cells

A
  • columnar w/ round, basal nucleus

- have prominent terminal web

27
Q

what is the otolithic membrane?

A

thick, gelatinous (glycoprotein) layer that contains small calcified particles (otoliths/otoconia)

28
Q

what is the function of the otolithic membrane?

A

detection of linear acceleration

29
Q

where do the semicircular ducts arise from?

A

the utricle

30
Q

what are the ampullae ?

A

dilated area of semicircular ducts near junction w/ utricle

31
Q

what are the cristae ampullares?

A

specialized sensory areas in ampullae that are similar to maculae but w/ thicker, cone-shaped glycoprotein layer (cupula) and NO OTOLITHS

32
Q

function of cristae ampullares

A

detect angular acceleration of the head along any of the three axes

33
Q

where does the endolymphatic duct lead?

A

to the endolymphatic sac

34
Q

lining of endolymphatic sac

A
  • columnar cells w/ irregular shaped nucleus

- columnar cells w/ long microvilli

35
Q

what might you find in the lumen of the endolymphatic duct and what is their function?

A

phagocytic cells (macrophages, neutrophils) - endolymph reabsorption

36
Q

what is the cochlear duct?

A
  • specialized area of saccule that has the spiral organ of Corti
  • surrounded above by scala vestibuli
  • surrounded below by scala tympani
37
Q

how do the scala vestibuli and scala tympani communicate with each other?

A

by a small hole near the cochlear apex called the helicotrema

38
Q

describe the basilar membrane of the cochlea

A

thick layer of amorphous material w/ keratin-like fibers

39
Q

describe tectorial membrane of cochlea

A

-makes contact w/ the processes of the hair cells

40
Q

what cells secrete tectorial membrane?

A

interdental cells of spiral sulcus

41
Q

describe the spiral organ of Corti

A
  • has hair cells and supporting cells
  • lies on basilar membrane
  • has inner tunnel of Corti and outer tunnel that communicate via intercellular spaces
42
Q

describe inner hair cells

A
  • organized in a single row along length of cochlear duct

- receive afferent synaptic terminals on basal surface

43
Q

describe outer hair cells

A
  • organized in 3-5 rows w/i a cup-shaped afferent nerve ending
  • stereocilia embedded in gelatinous tectorial membrane
44
Q

function of outer hair cells

A

sound reception and response to different sound frequencies

45
Q

describe inner and outer pillar cells

A
  • closely associated w/ each other
  • rest on basilar membrane
  • enclose and support inner tunnel of Corti
46
Q

describe inner and outer phalangeal cells

A
  • closely associated w/ inner and outer hair cells, respectively
  • support nerve fibers that form synapses w/ hair cells
47
Q

describe cells of Hensen and border cells

A

mark the inner and outer borders of the spiral organ of Corti

48
Q

describe how the ear functions for auditory purposes

A

sound strikes tympanic membrane -> vibration via ossicles, movement of stapes at oval window -> disturbs perilymph -> deflects basilar membrane in organ of Corti -> pillar cells on basilar membrane move laterally -> lateral shearing of stereocilia on sensory hair cells against tectorial membrane -> movement of stereocilia transduced into electrical impulses -> travels via cochlear nerve to brain

49
Q

describe how the ear functions for vestibular purposes

A

change in head position -> flow of endolymph in semicircular ducts (circular) or in saccules/utricles (linear):

  1. movement in semicircular canals -> displaces cupula overlying cristae ampullares -> bending of stereocilia on sensory hair cells
  2. movement in saccules/utricles -> displaces otoliths -> transmitted to the maculae via overlying gelatinous layer -> bending of stereocilia on sensory hair cells

movement of stereocilia transduced into electrical impulses -> transmitted to brain via vestibular nerve fibers

50
Q

what is nerve deafness?

A

lesion in nerves transmitting impulses from organ of Corti

51
Q

what can cause nerve deafness?

A
  • disease
  • drugs
  • prolonged loud noise
52
Q

what is conductive hearing loss?

A

hearing loss that occurs prior to oval window - defect in sound wave conduction

53
Q

what can cause conductive hearing loss?

A
  • inflammation (otitis media)

- otosclerosis in middle ear

54
Q

how can you test for conductive hearing loss?

A

using bone conduction: when a tuning fork is touched to head, vibrations conduct directly to the cochlea through bone

a person w/ only conductive hearing loss can detect tuning form sounds as well as someone w/ normal hearing

Histology - Exam 4 (5 decks)

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