Notes in Ear Development

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Published	10/28/2024	The external ear consists of the {{c1::pinna (or auricle)}}, {{c1::external auditory canal (ear canal)}}, and the {{c1::…
Published	10/28/2024	The middle ear contains:- {{c1::the auditory ossicles - the malleus, incus, and stapes - arranged in a chain in the tympanic …
Published	10/28/2024	The inner ear consists of the {{c1::cochlea}} and {{c1::vestibular apparatus}}
Published	10/28/2024	The {{c1::three semicircular canals, the utricle, and the saccule}} compose the vestibular apparatus
Published	10/28/2024	The derivatives of the inner ear are collectively known as the {{c1::membranous labyrinth}}.
Published	10/28/2024	The {{c2::inner ear}} develops from an {{c1::ectodermal otic placode}} that appears on either side of the neural tube at the level…
Published	10/28/2024	The {{c1::external and middle ears}} arise from the {{c2::first and second pharyngeal arches}} and the {{c2::first pharyngeal cleft and…
Published	10/28/2024	The internal ear is the {{c1::first::1st 2nd or 3rd}} of the three parts of the ear to develop. All of the inner ear derivatives arise from …
Published	10/28/2024	Week {{c2::3-4}}: The {{c1::otic placode}} appears on each side of the future hindbrain
Published	10/28/2024	The otic placode gradually invaginates to first form an {{c1::otic pit}}It then makes a closed, hollow {{c2::otic vesicle or otocyst}}, whic…
Published	10/28/2024	The {{c3::statoacoustic (vestibulocochlear) ganglion}} are derived from cells from {{c1:: the neural crests}} and {{c1::ventral otocyst…
Published	10/28/2024	The dorsomedial region of the {{c1::otic vesicle}} elongates to form an {{c2::endolymphatic appendage.}}
Published	10/28/2024	The distal portion of the endolymphatic appendage expands to form an {{c1::endolymphatic sac}} that is connected to the utricular part by a …
Published	10/28/2024	The rest of the otic vesicle (besides dorsomedial region that forms endolymphatic appendage) differentiates into:- a {{c1::pars superior (= dorsal, ut…
Published	10/28/2024	{{c2::Pars superior (utricular)}}: Forms the {{c1::semicircular canals.}}
Published	10/28/2024	The semicircular canals are oriented perpendicularly to each other and to consist of {{c1::anterior, posterior, and lateral semicircular}} canals duct…
Published	10/28/2024	A small expansion called the {{c1::ampulla}}, housing the sensory cells, forms at one end of each {{c2::semicircular canal.}}
Published	10/28/2024	The {{c1::pars superior}} also gives rise to the utricle (Fig).
Published	10/28/2024	The ventral tip of the {{c2::pars inferior}} elongates and coils, forming the {{c1::cochlear duct.}}
Published	10/28/2024	The cochlear duct penetrates the surrounding mesenchyme in a spiral fashion, until it completes the total {{c1::2.5::how many}} turns.
Published	10/28/2024	Cells of the cochlear duct differentiate to form the {{c1::spiral organ of Corti.}}
Published	10/28/2024	The {{c1::pars inferior}} also gives rise to the saccule.
Published	10/28/2024	Inductive influences from the {{c1::otic vesicle}} stimulate the mesenchyme around the {{c1::otic vesicle}} to condense and differentiate into a {{c2:…
Published	10/28/2024	As the membranous labyrinth enlarges, vacuoles appear in the {{c1::cartilaginous otic capsule}} and soon coalesce to form the {{c2…
Published	10/28/2024	The {{c1::cartilaginous otic capsule}} later ossifies to form the {{c2::bony labyrinth of the internal ear (part of the temporal bone)}}
Published	10/28/2024	The internal ear reaches its adult size and shape by the middle of the fetal period ({{c1::20-22::how many}} weeks).
Published	10/28/2024	The middle ear derivatives originate in the {{c1:: first and second pharyngeal (branchial) arches, first pharingeal pouch and firs…
Published	10/28/2024	The primordium of the tympanic membrane is the {{c1::first pharyngeal membrane.}}
Published	10/28/2024	In the embryo, the {{c1::pharyngeal membrane}} separates the {{c2::first pharyngeal groove}} from the {{c2::first pharyngeal pouch}}As development pro…
Published	10/28/2024	To summarize, the tympanic membrane develops from three main sources:- {{c1::Ectoderm of the first pharyngeal groove (outer lining).}}-…
Published	10/28/2024	{{c1::Infiltrated neural crest}} cells may contribute to mesenchyme of intervening layer. The {{c1::definitive tympanic membrane}} is formed…
Published	10/28/2024	Auditory tube and tympanic (middle ear) cavity form both from the {{c1::first pharyngeal pouch}}. The {{c1::first pharyngeal pouch}} el…
Published	10/28/2024	The{{c1:: proximal part of the tubotympanic recess}} forms the {{c2::pharyngotympanic tube (auditory tube or Eustachian tube)}}
Published	10/28/2024	The {{c1::distal part of the tubotympanic recess}} expands and becomes the {{c2::tympanic cavity}},
Published	10/28/2024	The malleus and incus arise from the {{c1::first pharyngeal arch}}
Published	10/28/2024	The stapes arises from the {{c1::second pharyngeal arch}}
Published	10/28/2024	The tensor tympani and the stapedius form in the {{c1::9th}} week
Published	10/28/2024	The tensor tympani (associated with the malleus) forms from {{c1::first pharyngeal arch mesoderm}}
Published	10/28/2024	The stapedius (associated with stapes) form from the {{c1::second-pharyngeal arch mesoderm }}
Published	10/28/2024	The tensor tympani muscle is innervated by {{c1::cranial nerve V}}The stapedius muscle is innervated by {{c1::cranial nerve VII}}
Published	10/28/2024	The precursor of the {{c1::external auditory meatus}} develops by an invagination of the {{c2::first pharyngeal cleft}} during the {{c2…
Published	10/28/2024	The {{c1::ectodermal}} lining of the deep portion of the primordial external auditory meatusProduces {{c2::meatal plug}} that comp…
Published	10/28/2024	The external auditory meatus does not achieve its final length until the age of {{c1::9 or 10}} years.
Published	10/28/2024	The {{c1::auricle}} develops from six {{c2::auricular hillocks (mesenchymal proliferations)}} that arise during the {{c3::5th}} week&nb…
Published	10/28/2024	Conductive hearing loss is the result of malformations in the {{c1::external and/or middle}} ear.
Published	10/28/2024	Sensorineural hearing loss can arise from defects in the {{c1::inner}} ear, {{c1::vestibulocochlear}} nerve, or the {{c1::auditory}} regions of t…
Published	10/28/2024	Defects of the external ear (i.e., the pinna or auricle) result from abnormal growth and morphogenesis of the {{c1::auricular hillocks}} derived …
Published	10/28/2024	{{c2::microtia}} = {{c1::small auricle}}
Published	10/28/2024	{{c1::anotia}} = {{c2::absence of the auricle}}
Published	10/28/2024	{{c1::Overgrowth of the hillocks}} results in {{c2::macrotia}}
Published	10/28/2024	Accessory hillocks may also form, producing {{c1::ectopic preauricular tags}}, which may or may not be accompanied by {{c1::preauricular pits}}
Published	10/28/2024	Defects of the middle ear result from abnormal formation or ossification of {{c1::the middle ear ossicles}}These are derived from {{c2:…
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