Ear Development Flashcards
When is the critical period for embryological development of the year?
B/w weeks 4 and 8
When does development of the ear occur?
Between wks 4 and 20
The medial part of the external ear came from what pharyngeal arch?
1st
The lateral part of the external ear came from what pharyngeal arch?
2nd
The mesenchymal swellings located within the pharyngeal arches are known as what?
Auricular hillocks
What are the cells that migrate and pull the surface ectoderm around to form the external ear?
Neural crest cells of the auricular hillocks
Auricular skin tags that may contain cartilage are a result of what?
Abnormal migration of surface ectoderm and neural crest cells
Abnormal or absent migration of the NCCs and auricular hillocks can result in what disorders?
Anotia
Microtia
What embryonic layer does the meatal plug arise from?
Surface ectoderm - 1st pharyngeal cleft
What embryonic layer does the inner ear arise from?
Surface ectoderm
What week does the inner ear begin to form?
Week 4
What embryonic structure gives rise to the membranous labyrinth?
Otic vesicle
Development of the utricle is dependent on what transcription factors?
DLX5 and DLX6
Lateral canal dependent on OTX1
What does the dorsal side of the otocyst give rise to?
Semicircular ducts and ampullae
Macula of utricle
Endolymphatic duct and sac
What does the ventral side of the otocyst give rise to?
Cochlear duct
Ductus reuniens
Maccula of saccule
Organ of Corti
What structure connects the cochlea to the vestibular apparatus?
Ductus reuniens
What is the embryonic layer that gives rise to the hair cells of the inner ear?
Surface ectoderm
Where are hair cells located in the inner ear?
Ampullae of semicircular canals
Macula of utricle
Organ of Corti (cochlea)
What CN is responsible for innervation to the inner ear?
CN VIII - Vestibulocochlear
What are the embryonic contributions to the vestibular ganglion?
Neural crest cells and surface ectoderm
What is the embryonic contribution to the spiral (cochlear ganglion)?
Surface ectoderm
What structures does the perilymphatic duct provide passage between?
Subarachnoid space to inner ear
What is the ion content of perilymph?
High Na
Low K and ptn
(Similar to CSF)
What is the ion content of endolymph?
High K and ptn
Low Na
(Similar to ICF)
What embryonic layer does the bony labyrinth arise from?
Mesoderm
In what week are the vacuoles of the bony labyrinth distinguishable as the scala vestibuli and scala tympani?
Week 8
In what week do the vacuoles of the bony labyrinth begin to form?
Week 6
What suspends the cochlear duct within the bony labyrinth and attaches it to the wall?
Spiral Ligament
What embryonic layer forms the tubotympanic recess?
Endoderm - 1st pharyngeal pouch
What bones of the middle ear arise from the 1st arch NCC?
Malleus and Incus
The stapes bone arises from what arch? What is the embryonic origin?
2nd arch
Neural crest
What embryonic layer does the epithelium covering the ossicles arise from?
Endoderm
What are the embryonic layers making up the tympanic membrane?
Ectoderm - from 1st pharyngeal cleft
Mesoderm
Endoderm - from 1st pharyngeal pouch
What pharyngeal arch does the tensor tympani M. arise from? What embryonic layer?
1st Pharyngeal arch
Mesoderm
What pharyngeal arch does the Stapedius M. arise from? What embryonic layer?
2nd pharyngeal arch
Mesoderm
What part of the fetal ear is affected if there is a maternal Rubella infection?
Inner ear - Spiral Organ/Organ of Corti defects
