Development of Ear
Embryologically ear can be divided into 3 parts-internal ear,middle ear,external ear.
Internal ear (ectoderm)
- First to develop in ear
- derived from surface ectoderm
- Specific thickening of surface ectoderm forms otic placode in early 4th week of intrauterine life
- In late 4 th week,otic placode invaginates into underlying mesenchyme to form otic pit and then otic vesicle
- otic vesicle has 2 portions-ventral saccular and dorsal utricle
- Ventral saccular forms saccule and cochlear duct
- Dorsal utricle forms utricle,endolymphatic duct,semicircular canals
- Full membranous ear is formed by 4th month of intrauterine life
- Adult size inner ear is formed by 5th month of IU life
Middle ear(endoderm)
- Development begins in 4th week and completed in 7th month
- Tympanic cavity,mastoid antrum and air cells are derived from endoderm pouch of 1st and 2nd branchial arch
- Dorsal part endodermal pouch of 1st and 2nd branchial arch forms tubotympanic tube.Proximal part of this tube forms Eustachian tube and distal portion middle ear cavity and antrum
- Incus and malleus from 1st branchial arch
- Stapes from 2nd branchial arch except its foot plate and annulus which are from otic capsule
External ear
- From dorsal part of ectodermal cleft of 1st branchial arch
- 3 structures-PEE i.e.pinna,external auditory canal and ear drum
- Ear drum is derived from all 3 germ layers
