File:Adult hearing embryonic origins.jpg

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Adult Hearing Embryonic Origins

Many different embryonic components contribute to the sensory structures required for hearing. It is always considered/divided in terms of the 3 main divisions (external, middle and inner), each of which have their own separate components from different embryonic origins.

The complexity and time course of development leads to many associated abnormalities.

External Ear

Auricle - Pharyngeal Arches 1 and 2 (ectoderm, mesoderm)
- form from 6 hillocks (week 5) 3 on each of arch 1 and 2
External Auditory Meatus - Pharyngeal Arch 1 groove or cleft (ectoderm)
Tympanic Membrane - Pharyngeal Arch 1 membrane (ectoderm, mesoderm, endoderm)

Middle Ear

Middle Ear Ossicles
- Malleus and incus - Pharyngeal Arch 1 cartilage Neural crest (ectoderm)
- Stapes - Pharyngeal Arch 2 cartilage Neural crest (ectoderm)
Middle Ear Muscles
- Tensor tympani - Pharyngeal Arch 1 (mesoderm)
- Stapedius - Pharyngeal Arch 2 (mesoderm)
Middle ear cavity - Pharyngeal Arch 1 pouch (endoderm)

Inner Ear

Inner Ear Labyrinth
- Cochlea - Otic vesicle - Otic placode (ectoderm)
- Semicircular canals - Otic vesicle - Otic placode (ectoderm)
- Saccule and utricle - Otic vesicle - Otic placode (ectoderm)
Cranial Nerve VIII
- Auditory component - Otic vesicle and neural crest (ectoderm)
- Vestibular component - Otic vesicle and neural crest (ectoderm)

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	Date/Time	Thumbnail	Dimensions	User	Comment
current	23:55, 27 September 2009		1,000 × 675 (80 KB)	S8600021 (talk \| contribs)

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