Ear dev. 43

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Development of the Ear

Jittipan Chavadej, Ph.D.Anatomy Dept., Fac. of Science

Mahidol University

 yr.,2000

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Matre components of the ears

!he ear is composed of inner,middle and oter ear portions

•

 oter ear "aricle

"e#t. aditory meats  "tympanic mem$rane

•

 middle ear " malles, incs % stapes  " aditory t$e

• inner ear  " cochlear dct

  " semicirclar canal

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Formation of the ear

Dal ori&in

" thic'ened ectodermalplacode at rhom$encephalon

" first and second $ranchialarches

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(hom$encephalonre&ion)formation

of otic vesicles

Derivatives of

the *st % +nd $ranchial arches

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Development of inner ear

ndction " rhom$encephalon-srfaceectoderm

tic placode tic vesicle

Dorsal vesti$larre&ion

/entral cochlearre&ion

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(hom$encephalonre&ion)otic placode ,otic pit and oticvesicle

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/entral cochlear re&ion 

Saccle  Cochlear dct

D o r s a l  ve s t i $ l a r  r e  & i o n 

Utricle Semicirclarcanals

Endolymphatic

dct

Membranous labyrinth

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Development of the otic vesicle sho0in& a dorsal triclarportion 0ith endolymphatic dct, and a ventral sacclarportion

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Saccule, cochlea & organ of Corti

t&ro0th of cochlear dct"spiralfashion 1th 0'." +*2+ trns

Cochlear dct conect 0ith saccle

thro&h dcts reniens

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Cochlear duct 3 mesenchyme 

Scala mediaCartila&eos shell

Scala vesti$li Scala tympani

/esti$lar mem.4asilar mem.

r&an of Corti5S.media % S.vesti$li6 

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Development of the scala tympani % scala vesti$li

7ote)the aditory nerve and spiral &an&lion

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Scala media " or&an of Corti

8air cells !ectorial mem.

gelatineous substance!9ateral 0all"spiral li&ament

Medial " modiols

  " spiral &an&lion

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Development of the or&an of Corti

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Semicircular canals & "tricle

/esti$lar portion"central portionappose to each other  disappearance

: semicirclar canals

Crs ampllare"crista ampllaris

Utricle%Saccle"maclae acosticae

Statoacostic &an&lion C7 /

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Development of the semicirclar canals

7ote)disappearance of the central portion % the ampllae

in the semicirclar canals 

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Development of the Middle #ar

E#pansion of *st pharyn&eal pochmiddle cavity % aditory t$e

;;9inin&" endodermal ori∈;

+nd mo."$lind end oft$otympanict$e *st pharyn&eal cleft

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Development of the middle ear

7ote)t$otympanic recess, mesenchymal condensation ear

ossicle formation 

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<th0'."condensation of mesenchyme 5mesoderm6)jst dorsal to the end of t$otympanic

end ear ossicles

!ympanic cavity"ear ossicles inloose mesenchyme latepre&nancy) pro&rammed cell death 

sspension of ear ossicles+ mo. after $irth"free movement

of ear ossicles

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Development of the ear ossicles in the tympanic cavity

7ote) malles contact 0ith eardrm, stapes contact 0ithoval 0indo0 and endodermal epithelim of tympanic cavity

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Dal ori&in of ear ossicles

•

malles % incs"mesoderm of *st

 $ranchial arch

•

stapes"mesoderm of +nd

 $ranchialarch

;!ensor tympani ms." C7 /;Stapedis " C7 / 

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Development of the #$ternal #ar

Pinna " mesenchyme of *st %+nd $ranchial arches)+nd mo. ariclar

hilloc' enlar&ement5asymmetry6

E#ternal aditory meats " in0arde#pansion of the *st $ranchial cleft

:rd"meatal pl&5solid epith. plate6

=th"dissoltion of meatal pl&

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9ateral vie0 of the head sho0in& the si# ariclar hilloc'ssrrondin& the dorsal end of the *st pharyn&eal cleft

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Con&enital malformation of the ear

•Con&enital deafness"inner eardeafness5r$ella6,middle ear

deafness 5*st % +nd arches6,a&enesisof e#ternal ear

•Ariclar anomalies

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!8E

E7D