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AUDE 5310 Embryology & Genetic Conditions > Auditory System Development > Flashcards

Auditory System Development Flashcards

1
Q

mesoderm forms

A

ossicles, temporal bone and bony labyrinth

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2
Q

Ectoderm forms

A

outer ear (skin), inner ear (sense organs) & membranous labyrinth

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3
Q

endoderm forms

A

middle ear epithelial lining, aerated mastoid cavities & eustachian tube

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4
Q

During embryologic development, six hillocks of tissue form around both sides of the first branchial groove. What do these hillocks eventually become?

A

pinna of external ear

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5
Q

Which branchial arches play a major role in development of ear structures?

A

1 & 2

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6
Q

Embryologically, the central nervous system (including the brain and spinal cord), sense organs such as the cochlear and vestibular hair cells, and the skin are derived from which of the germ layers?

A

ectoderm

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7
Q

What is the generic term that describes defects of the spinal cord, during embryologic development when the caudal neuropore does not properly close?

A

spina bifida

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8
Q

With respect to neuroembryology, the term gastrulation refers to

A

formation of 3 germ layers

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9
Q

During embryologic development, which germ layer gives rise to the skeletal structures, circulation structures, meninges, and cartilage (including the ossicles and temporal bone)?

A

mesoderm

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10
Q

Embryologically, development of the inner ear begins with formation of…

A

otic placodes which are thickenings of ectoderm

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11
Q

During embryologic development, what does the tubotympanic recess eventually become?

A

ear canal and ™

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12
Q

Which branchial arches play a major role in development of ear/auditory structures?

A

1 & 2

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13
Q

describe inner ear formation in overview

A

First trimester
Ectoderm Auditory/otic placode on sides of neural tube—3rd week
Otic pits to auditory vesicle to otocyst
Saccular elongation grows and spirals into cochlea, SCC form,
SCC done first, cochlea last, cartilage first then ossifying
2.5 coils should be completed, the sensory and supporting cells and connections
Adult appearance by 20th to 23rd week (fetal midterm)
Statoacoustic ganglion
CNS development and neural connections and myelin continue to develop

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14
Q

inner ear development is mostly in ____ trimester with mature appearance by ____

A

first, 20-23 weeks

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15
Q

when does the otic placoe form

A

3rd week, 21 days

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16
Q

what is the otic placode

A

superficial thickening of surface ectoderm on either side of the open neural tube

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17
Q

ectoderm will become the____ of the inner ear

A

epithelium

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18
Q

the migrating neural cells aid in formation of

A

external ear
middle ear (ossicles)
inner ear (otic capsule and sensory neurons)

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19
Q

what happens on the 23rd day for inner ear

A

otic placod invaginates to become the otic pit

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20
Q

what happens by day 30 for inner ear

A

pit closes to form otocyst/auditory vesicle located dorsal to the 2nd pharyngeal cleft
neural tube closed now
otocyst differentiates into vestibular and cochlear portions

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21
Q

what is otic induction

A

time frame from the ectodermal thickening adjacent to the rhombencephalon on day 22-23 til complete invagination of the otic vesicle around day 26

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22
Q

what happens in the 4th week for inner ear

A

otic vesicle splits from the surface ectoderm dividing into the ventral and dorsal portion

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23
Q

what does the ventral portion of otic vesicle split into

A

saccule (part of vestib)
cochlear duct (future scala media and organ of corti)

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24
Q

what does the dorsal portion of otic vesicle split into

A

future utricle & semicircular canals (part of vestib system)
endolymphatic duct

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25
Q

what do we see in 6 week for inner ear

A

saccule forms tubular shaped pocket in lower pole
rudimentary cochlear duct, epnetrating surrounding mesenchyme in a spiral fashion to form the cochlea

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26
Q

cochlea completes its 2 3/4 turns by

A

end of 8th week

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27
Q

utricle and saccule communicate indirectly through

A

utriculosaccular duct

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28
Q

what system came first in inner ear

A

vestibular because cochlea develops from the saccule

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29
Q

what is significant of the otic capsule

A

necessary for proper development of the inner ear and for housing the perilymphatic fluid

cartilaginous otic capsule will eventually become the petrous portion of the temporal bone and called the bony labyrinth

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30
Q

what forms the cartilaginous otic capsule in week 9

A

the mesenchyme surrounding the inner ear membranous labyrinth

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31
Q

how does the auditory nerve form

A

from the neural crest cells

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32
Q

auditory nerve peirces the otic capsule where

A

two divisions
one for vestib and one for cochlea

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33
Q

cartilage surrouding cochlear duct forms

A

scala vestibuli
scala tympani

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34
Q

two perilymphatic spaces in the cochlea

A

scala vestibuli
scala tympani

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35
Q

The cochlear duct or scala media is separated from

A

scala vestibuli by the Reissner’s or vestibular membrane
scala tympani by the basilar membrane

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36
Q

when do sensory epithelia develop in cochlea

A

During week 7 to 8 of gestation, the cochlea exits the cell cycle and they begoin

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37
Q

2 ridges from epithelial cells of the cochlear duct

A

inner ridge will form the future spiral limbus

outer ridge will give rise to
about 3 rows of OHC
about 1 row of IHC

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38
Q

Epithelial cells of the spiral limbus form the ______ that lies over the tips of the outer hair cells

A

tectorial membrane

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39
Q

At about end of the ____ month of gestation, the human cochlea is developed and functional

A

5

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40
Q

when is the cochlea fully developed and functional

A

end of the 5th month

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41
Q

appear as flattened out-pockets of the utricular portion of the otic vesicle

A

semicircular canals, About the 6th week of development,

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42
Q

containing sensory cells for equilibrium and balance

A

crus ampullare

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43
Q

where are the crus ampullare

A

at the end of each canal

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44
Q

waht are filled with endolymph

A

semicircular canals, utricle and saccule

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45
Q

three canals are covered by

A

bone

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46
Q

Fluid between the outer bony covering and the semicircular canals

A

perilymph

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47
Q

three semicircular canals are sensitive to

A

angular motion or rotation as experienced when turning the head

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48
Q

macculae in the utricle and saccule are very sensitive to

A

linear acceleration as when the body or head is tilted

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49
Q

____ & ____ are gravistatic end organs (responsive to gravity)

A

utrticle and saccule

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50
Q

when you turn your head why dont you get dizzy?

A

scc are there to keep head and body upright

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51
Q

looking down and bending over?

A

utricle and saccule

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52
Q

where are the otoliths?

A

utricle and saccule

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53
Q

hearing loss can either be

A

isolated condition (non-syndromic) or associated with other abnormalities/disorders (syndromic)

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54
Q

isolated condition

A

non syndromic

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55
Q

associated with other abnormalities/disorders

A

syndromic

56
Q

undergo complex development because of the actions of a myriad of genes

A

inner ear
both cochlea and vestib

57
Q

In many instances the hearing and or vestibular problems in the embryologic phase are caused by

A

single gene (monogenic) mutations and/or interactions between multiple genes

58
Q

why is our knowledge in molecular basis of inner ear development important

A

It is incomplete but necessary to some day fully understand how the inner ear develops and perhaps prevent/treat gene mutations that can lead to auditory/vestibular disorders

59
Q

Describe the inner ear formation at week 3

A

The first part of the inner ear to form is the otic placode (superficial thickening of surface ectoderm located on either side of the open neural tube).
Otic placodes sink inward and become otic pits. The otic pit is located dorsal to the second pharyngeal cleft.

60
Q

Describe inner ear formation at week 4

A

The neural tube should be closed by now.
The otic pit closes with its edges fused to form the otocyst.
The otocyst turns into the membranous labyrinth.

61
Q

what happens during week 6-8 of inner ear

A

Otocyst continues to divide into the vestibular and cochlear portions.
Ventral part of the otocyst gives rise to the saccule and cochlear duct.
Dorsal part of the otocyst gives rise to the utricle, semicircular canals, and endolymphatic duct.
Cochlea begins to coil.

62
Q

what happens to inner ear during week 7-12

A

Cochlea’s 2.5 coils are completed and the 3 semicircular canals have formed.
Sensory and supporting cells are developing in vestibular and cochlear sensory end organs.
By month 3, the otic capsule begins ossifying. The vestibular end organs are primary and complete before the cochlea. This is why we see more cochlea developmental deviations than in the vestibular.

63
Q

gives rise to the stapes

A

arch 2

64
Q

gives rise to the mandible

A

arch 1

65
Q

external humps

A

arches

66
Q

external

A

clefts/grooves

67
Q

internal

A

pouches

68
Q

clefts grooves

A

ectoderm

69
Q

mesenchyme

A

core

70
Q

pouches

A

endoderm

71
Q

Each arch will have its own

A

cartilage, nerve, muscle and artery

72
Q

endoderm invaginates and creates

A

eustachian tube

73
Q

ectoderm invaginates and creates

A

EAC

74
Q

site where the canal and pouch meet is the

A

TM

75
Q

branchial arches form at ___ days post conception

A

22

76
Q
A
77
Q

critical for face outer and middle ear development

A

1 and 2 arch

78
Q

formsexternal and middle ear

A

1 and 2 pharyngeal arches, pouches and clefts and neural crest cells

79
Q

develops into facial and auditory muscles

A

mesoderm of arches

80
Q

endoderm =

A

pouches

81
Q

ectoderm =

A

clefts/grooves

82
Q

formation begins during week 6 with invagination of the 1st pharyngeal cleft

A

EAC

83
Q

is the ear canal fully formed when baby is born?

A

no takes about 6-7 years until it is fully developed

84
Q

2nd 3rd and 4th clefts/grooves form the_______, later disappears

A

cervical sinus

85
Q

If the cervical sinus persists, it forms the

A

lateral or branchial cysts or fistulas

86
Q

marks boundary between outer and middle ear

A

TM

87
Q

outer layer is formed by the

A

ectodermal meatual plug of the EAC

88
Q

middle layer is mesoderm derived from

A

neural crest cells

89
Q

inner layer is endoderm the

A

epithelial lining of the tympanic cavity

90
Q

formed by the tubotympanic recess - extension of the first pharyngeal pouch

A

tympanic cavity and ET

91
Q

extension of the first pharyngeal pouch

A

tubotympanic recess

92
Q

tubotympanic recess is derived from

A

endoderm

93
Q

proximal extension of the first pouch

A

future eustachian tube

94
Q

distal extension of first pouch

A

future tympanic cavity

95
Q

what clears mucus and pathogens out of the ME cavity?

A

motile silica push it out into the throat through the eustachian tube

96
Q

clears ME of mucus and pathogens through the eustachian tube to the mouth

A

cilia

97
Q

neural crest cells play a role in development of these

A

cilia

98
Q

ME infection arises when

A

cilia breaks down and there is not movement of fluid in the ME

99
Q

develop independently from each other from tubotympanic recess with neural cell contribution

A

ossicles

100
Q

derived from the 1st and 2nd pharyngeal arches

A

ossicles

101
Q

are the 3 ossicles from the same arches?

A

no from different arches

102
Q

ossicles are made up of

A

cartilage and embedded in mesenchyme adjacent to the tympanic cavity

103
Q

during ____ month of gestation, tympanic cavity envelops the ossicles

A

8

104
Q

what is the lever system form the ossicles

A

diminish the force of sound waves in the ME and increase force of sound waves on the inner ear

105
Q

Most of the head and neck develops from

A

the pharyngeal arches

106
Q

Each arch has _____ on the outside, ____ on the inside, and a ____ core

A

ecto, endo, meso

107
Q

The mesodermal core develops a cartilage/boney component after being invaded by

A

neural crest cells, a cranial nerve component, and a vascular component (aortic arch arteries)

108
Q

Externally, there is a pharyngeal ____ between each pair of pharyngeal arches

A

cleft/groove

109
Q

The clefts go through a sequence of development that when goes awry, can lead to

A

cervical or branchial fistulas and cysts

110
Q

Internally, there is a pharyngeal ____ between each pair of pharyngeal arches

A

pouch

111
Q

These endodermal pouches contribute to development of the

A

tympanic membrane, tonsils, thymus gland, parathyroid glands and parafollicular cells of thyroid gland

112
Q

explains the sensory innervation of the face

A

relationships of these prominences to the trigeminal nerve

113
Q

explain the varieties of cleft lip and cleft palate

A

Failures of fusion of pairs of these prominences

114
Q

what are bony, muscle and nerve derivatives of the first arch

A

Bony: Maxillary bone, zygomatic bone, temporal bone, mandible, malleus, and incus

Muscle: Muscles of mastication, mylohyoid muscle, anterior belly of digastric, tensor tympani, tensor palatine muscle

Trigeminal nerve (V)

115
Q

what are bony, muscle and nerve derivatives of the second arch

A

Bony:Stapes, styloid process, lesser horn of the hyoid bone, and upper portion of body of the hyoid bone

muscle: Muscles of facial expression, posterior belly of digastric, stylohyoid, stapedius

Facial nerve (VII)

116
Q

what are bony, muscle and nerve derivatives of the third arch

A

bony:Greater horn of the hyoid bone, lower portion of body of the hyoid bone
Muscle: Stylopharyngeus muscle
Glossopharyngeal nerve (IX)

117
Q

what are bony, muscle and nerve derivatives of the fourth arch

A

Bony: Laryngeal cartilages
Muscle: Cricothyroid muscle, levator palatine muscle, pharyngeal constrictors, intrinsic muscles of the larynx
Vagus nerve (X)

118
Q

what are the derivatives of the first pouch

A

eustachian tube and middle ear cavity

119
Q

what are the derivatives of the second pouch

A

lining of palatine tonsils

120
Q

what are the derivatives of the first cleft/groove

A

develops into external auditory meatus
defects here can result in preauricular cysts or fisutulas

121
Q

Ectoderm forms

A

skin covering

122
Q

Mesoderm forms

A

cartilage of external ear

123
Q

Most of auricle from the ____ branchial arch

A

second

124
Q

Tragus from the ____ branchial arch

A

first

125
Q

Pinna continues to grow until about

A

age 9

126
Q

hillocks are located between ___ and ___ arches, 3 on each side of the ear canal

A

fisrt, second

127
Q

During the 5th week the hillocks arise on the

A

branchial clefts

128
Q

By the 7th week the hillocks enlarge and fuse to form ______

A

auricle/pinna

129
Q

Pinna formation is completed at

A

~ 30 weeks

130
Q

stem cells, can develop into anything, on sides of neural tube

A

neural crest cells

131
Q

why can human babies not walk/talk when they are born?

A

maturation - they dont do these because cns and pns haven’t matured yet, synapses and schwann is not fully developed yet

132
Q

why we see so many deviations of pinna

A

there is a multitude of genes that form the pinna

133
Q

no two pinnas are the same

A

true

134
Q

3 projections on the 1st pharyngeal cleft

A

tragus, helix, cymba concha

135
Q

3 projections from the 2nd pharyngeal cleft

A

antitragus antihelix, concha

AUDE 5310 Embryology & Genetic Conditions (18 decks)

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