Ear development Flashcards
The inner ear develops from
ectodermal otic placode
The external and middle ears arise from
first and second pharyngeal arches and the first pharyngeal cleft and pouch.
When does the Otic Placode first appear?
Week 3-4
The otic placode gradually invaginates to first form
the Otic Pit
then
the Otic Vesicle
Young neurons delaminate from the ventral otocyst to form
statoacoustic (vestibulocochlear) ganglion
statoacoustic (vestibulocochlear) ganglion Splits into?
cochlear and vestibular portions.
Otic Vesicle divides into three things
endolymphatic sac
pars superior (= dorsal, utricular part)
pars inferior (= ventral, saccular part)
Pars superior (utricular): Forms
Semisicular Canals
Ampulla
Urticle
Pars inferior (saccular) Forms
cochlear duct
spiral organ of Corti
saccule
mesenchyme around the otic vesicle to condense and differentiate into
cartilaginous otic capsule
vacuoles appear in the cartilaginous otic capsule
- Which coelse to form perilymphatic space
- Membranus labrinth floats in Perilymph
- Perilymphatic space is comunication with the sub achachnoid space.
The cartilaginous otic capsule later ossifies to form
bony labyrinth of the internal ear (part of the temporal bone).
When does the inner ear reach its adult size?
middle of the fetal period (20-22 weeks)
The tympanic membrane is made up of what types of cells?
Ectoderm of the first pharyngeal groove (outer lining). Endoderm of the tubotympanic recess (inner lining). Mesenchyme (connective tissue) that form the intervening layer between the outer and inner lining. neural crest cells
The first pharyngeal pouch elongates to form:
tubotympanic recess
proximal part of the tubotympanic recess forms the
pharyngotympanic tube (auditory tube or Eustachian tube)
The distal part of the tubotympanic recess expands and becomes the?
tympanic cavity
- which gradually wraps around the small bones of the middle ear-auditory ossicles (malleus, incus, and stapes), their tendons and ligaments, and the chorda tympani nerve
- occures late in pregnancy, 8th month
The malleus and incus arise from
First pharyngeal Arch