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

Auditory System Development Flashcards

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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
what do we see in 6 week for inner ear
saccule forms tubular shaped pocket in lower pole rudimentary cochlear duct, epnetrating surrounding mesenchyme in a spiral fashion to form the cochlea
26
cochlea completes its 2 3/4 turns by
end of 8th week
27
utricle and saccule communicate indirectly through
utriculosaccular duct
28
what system came first in inner ear
vestibular because cochlea develops from the saccule
29
what is significant of the otic capsule
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
30
what forms the cartilaginous otic capsule in week 9
the mesenchyme surrounding the inner ear membranous labyrinth
31
how does the auditory nerve form
from the neural crest cells
32
auditory nerve peirces the otic capsule where
two divisions one for vestib and one for cochlea
33
cartilage surrouding cochlear duct forms
scala vestibuli scala tympani
34
two perilymphatic spaces in the cochlea
scala vestibuli scala tympani
35
The cochlear duct or scala media is separated from
scala vestibuli by the Reissner’s or vestibular membrane scala tympani by the basilar membrane
36
when do sensory epithelia develop in cochlea
During week 7 to 8 of gestation, the cochlea exits the cell cycle and they begoin
37
2 ridges from epithelial cells of the cochlear duct
inner ridge will form the future spiral limbus outer ridge will give rise to about 3 rows of OHC about 1 row of IHC
38
Epithelial cells of the spiral limbus form the ______ that lies over the tips of the outer hair cells
tectorial membrane
39
At about end of the ____ month of gestation, the human cochlea is developed and functional
5
40
when is the cochlea fully developed and functional
end of the 5th month
41
appear as flattened out-pockets of the utricular portion of the otic vesicle
semicircular canals, About the 6th week of development,
42
containing sensory cells for equilibrium and balance
crus ampullare
43
where are the crus ampullare
at the end of each canal
44
waht are filled with endolymph
semicircular canals, utricle and saccule
45
three canals are covered by
bone
46
Fluid between the outer bony covering and the semicircular canals
perilymph
47
three semicircular canals are sensitive to
angular motion or rotation as experienced when turning the head
48
macculae in the utricle and saccule are very sensitive to
linear acceleration as when the body or head is tilted
49
____ & ____ are gravistatic end organs (responsive to gravity)
utrticle and saccule
50
when you turn your head why dont you get dizzy?
scc are there to keep head and body upright
51
looking down and bending over?
utricle and saccule
52
where are the otoliths?
utricle and saccule
53
hearing loss can either be
isolated condition (non-syndromic) or associated with other abnormalities/disorders (syndromic)
54
isolated condition
non syndromic
55
associated with other abnormalities/disorders
syndromic
56
undergo complex development because of the actions of a myriad of genes
inner ear both cochlea and vestib
57
In many instances the hearing and or vestibular problems in the embryologic phase are caused by
single gene (monogenic) mutations and/or interactions between multiple genes
58
why is our knowledge in molecular basis of inner ear development important
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
Describe the inner ear formation at week 3
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
Describe inner ear formation at week 4
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
what happens during week 6-8 of inner ear
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
what happens to inner ear during week 7-12
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
gives rise to the stapes
arch 2
64
gives rise to the mandible
arch 1
65
external humps
arches
66
external
clefts/grooves
67
internal
pouches
68
clefts grooves
ectoderm
69
mesenchyme
core
70
pouches
endoderm
71
Each arch will have its own
cartilage, nerve, muscle and artery
72
endoderm invaginates and creates
eustachian tube
73
ectoderm invaginates and creates
EAC
74
site where the canal and pouch meet is the
TM
75
branchial arches form at ___ days post conception
22
76
77
critical for face outer and middle ear development
1 and 2 arch
78
formsexternal and middle ear
1 and 2 pharyngeal arches, pouches and clefts and neural crest cells
79
develops into facial and auditory muscles
mesoderm of arches
80
endoderm =
pouches
81
ectoderm =
clefts/grooves
82
formation begins during week 6 with invagination of the 1st pharyngeal cleft
EAC
83
is the ear canal fully formed when baby is born?
no takes about 6-7 years until it is fully developed
84
2nd 3rd and 4th clefts/grooves form the_______, later disappears
cervical sinus
85
If the cervical sinus persists, it forms the
lateral or branchial cysts or fistulas
86
marks boundary between outer and middle ear
TM
87
outer layer is formed by the
ectodermal meatual plug of the EAC
88
middle layer is mesoderm derived from
neural crest cells
89
inner layer is endoderm the
epithelial lining of the tympanic cavity
90
formed by the tubotympanic recess - extension of the first pharyngeal pouch
tympanic cavity and ET
91
extension of the first pharyngeal pouch
tubotympanic recess
92
tubotympanic recess is derived from
endoderm
93
proximal extension of the first pouch
future eustachian tube
94
distal extension of first pouch
future tympanic cavity
95
what clears mucus and pathogens out of the ME cavity?
motile silica push it out into the throat through the eustachian tube
96
clears ME of mucus and pathogens through the eustachian tube to the mouth
cilia
97
neural crest cells play a role in development of these
cilia
98
ME infection arises when
cilia breaks down and there is not movement of fluid in the ME
99
develop independently from each other from tubotympanic recess with neural cell contribution
ossicles
100
derived from the 1st and 2nd pharyngeal arches
ossicles
101
are the 3 ossicles from the same arches?
no from different arches
102
ossicles are made up of
cartilage and embedded in mesenchyme adjacent to the tympanic cavity
103
during ____ month of gestation, tympanic cavity envelops the ossicles
8
104
what is the lever system form the ossicles
diminish the force of sound waves in the ME and increase force of sound waves on the inner ear
105
Most of the head and neck develops from
the pharyngeal arches
106
Each arch has _____ on the outside, ____ on the inside, and a ____ core
ecto, endo, meso
107
The mesodermal core develops a cartilage/boney component after being invaded by
neural crest cells, a cranial nerve component, and a vascular component (aortic arch arteries)
108
Externally, there is a pharyngeal ____ between each pair of pharyngeal arches
cleft/groove
109
The clefts go through a sequence of development that when goes awry, can lead to
cervical or branchial fistulas and cysts
110
Internally, there is a pharyngeal ____ between each pair of pharyngeal arches
pouch
111
These endodermal pouches contribute to development of the
tympanic membrane, tonsils, thymus gland, parathyroid glands and parafollicular cells of thyroid gland
112
explains the sensory innervation of the face
relationships of these prominences to the trigeminal nerve
113
explain the varieties of cleft lip and cleft palate
Failures of fusion of pairs of these prominences
114
what are bony, muscle and nerve derivatives of the first arch
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
what are bony, muscle and nerve derivatives of the second arch
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
what are bony, muscle and nerve derivatives of the third arch
bony:Greater horn of the hyoid bone, lower portion of body of the hyoid bone Muscle: Stylopharyngeus muscle Glossopharyngeal nerve (IX)
117
what are bony, muscle and nerve derivatives of the fourth arch
Bony: Laryngeal cartilages Muscle: Cricothyroid muscle, levator palatine muscle, pharyngeal constrictors, intrinsic muscles of the larynx Vagus nerve (X)
118
what are the derivatives of the first pouch
eustachian tube and middle ear cavity
119
what are the derivatives of the second pouch
lining of palatine tonsils
120
what are the derivatives of the first cleft/groove
develops into external auditory meatus defects here can result in preauricular cysts or fisutulas
121
Ectoderm forms
skin covering
122
Mesoderm forms
cartilage of external ear
123
Most of auricle from the ____ branchial arch
second
124
Tragus from the ____ branchial arch
first
125
Pinna continues to grow until about
age 9
126
hillocks are located between ___ and ___ arches, 3 on each side of the ear canal
fisrt, second
127
During the 5th week the hillocks arise on the
branchial clefts
128
By the 7th week the hillocks enlarge and fuse to form ______
auricle/pinna
129
Pinna formation is completed at
~ 30 weeks
130
stem cells, can develop into anything, on sides of neural tube
neural crest cells
131
why can human babies not walk/talk when they are born?
maturation - they dont do these because cns and pns haven’t matured yet, synapses and schwann is not fully developed yet
132
why we see so many deviations of pinna
there is a multitude of genes that form the pinna
133
no two pinnas are the same
true
134
3 projections on the 1st pharyngeal cleft
tragus, helix, cymba concha
135
3 projections from the 2nd pharyngeal cleft
antitragus antihelix, concha

AUDE 5310 Embryology & Genetic Conditions (18 decks)

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