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Ear Embryology, Auricle Malformations Failure of 1 arch to form EAM -…
Ear Embryology
Middle Ear
Loose mesenchyme dissolves
1 Arch: Malleus, Incus,
Tensor tympani m (CN V)
2 Arch Stapes
Stapedius m (CN VII)
1 Pouch
Middle ear cavity/auditory tube
Tympanic antrum formed via
vacuolization
Infancy -->
Endodermal epithelium dissolves bone
creates mastoid air cells
External Ear
1 Cleft
(External Acoustic Meatus)
Meet and separate
external from middle
Mensechymal layers
(neural crest
paraxial mesoderm)
Tympanic Membrane
•Surface Ectoderm
•Mesenchyme
•Endoderm
External Acoustic Meatus
Ectoderm at the bottom of meatus
forms meatal plug
Month 7 disintegrates & ectodermal floor forms
external part of tympanic membrane
1 Arch &
2 Arch
Neural Crest Mesenchyme
Surround 1 Cleft
Auricular Hillocks
Auricle
Neural Crest
Internal Ear
Surface Ectoderm Thickens
Otic Placode-->Otic Pit
-->
Otic Vesicle
Ganglion cells
Statoacoustic
Vestibulochochlear ganglia
Vestibular n
Cochlear n
Ventral Saccule
Vertical Accel
-->cochlear duct
Membranous Labyrinth
Contains Perilymph
Saccule and Utricle
have Maculae -->smiliar function to crista ampullaris
Remains connected by
ductus reuniens
Inferior Part
Elongates
Cochlear duct
(mesenchyme) & wraps around
2.5 times by week 8
Cells-->
Spiral organ of corti
Mesenchyme surrounding cochlear duct
differentiates into cartilage
Remains attached by
Spiral ligament (laterally)
1 more item...
Medial Aspect connected
to modiolus
Makes central axis
Dorsal Utricle (horizontal accel)
Semicrcular canals
Endolympathic duct
Out pockets appear --->
Three semircular canals
One end forms crus noampullare
(does not expand)
Crus ampullare
{one end/cannal)
Expands
Crista Ampullaris
(sensory cells for eq)
Auricle Malformations
Failure of 1 arch to form EAM
--> forms pits
Conductive Hearing Loss
Neurocrest cells
Also contirbute
Hearing Comes
From Here
Sensorineural Hearing Loss
Hair cells/Auditory
Nerve Ganglia
Congenital Deafness
Failure of Meatal plug to dissolve