1. Anatomy Dept., Fac. of Science Mahidol University
Development of the Ear
Jittipan Chavadej, Ph.D.
Anatomy Dept., Fac. of Science Mahidol University
yr.,2000

2. Mature components of the ears
The ear is composed of inner, middle and outer ear portions
outer ear -auricle
-ext. auditory meatus
-tympanic membrane
middle ear - malleus, incus & stapes
- auditory tube
inner ear - cochlear duct
- semicircular canal

3. Formation of the ear Dual origin - thickened ectodermal
placode at rhombencephalon
- first and second branchial
arches

4. Rhombencephalon region:formation of otic vesicles
Derivatives of the 1st & 2nd branchial arches

5. Development of inner ear
Induction - rhombencephalon~surface ectoderm
Otic placode Otic vesicle
Dorsal vestibular region
Ventral cochlear region

6. Rhombencephalon region:otic placode , otic pit and otic vesicle

7. Membranous labyrinth Ventral cochlear region Saccule Cochlear duct
Dorsal vestibular region
Utricle
Semicircular
canals
Endolymphatic
duct

8. Development of the otic vesicle showing a dorsal utricular portion with endolymphatic duct, and a ventral saccular portion

9. Saccule, cochlea & organ of Corti
Outgrowth of cochlear duct-spiral fashion 8th wk.- 21/2 turns
Cochlear duct conect with saccule through ductus reuniens

10. Cochlear duct + mesenchyme
Cartilageous shell
Scala media
Scala tympani
Scala vestibuli
Basilar mem.
Vestibular mem.
(S.media & S.vestibuli)
Organ of Corti

11. Development of the scala tympani & scala vestibuli
Note:the auditory nerve and spiral ganglion

12. Scala media - organ of Corti
Hair cells
Tectorial mem. (gelatineous substance)
Lateral wall-spiral ligament
Medial - modiolus
- spiral ganglion

13. Development of the organ of Corti

14. Semicircular canals & Utricle
Vestibular portion-central portion appose to each other disappearance semicircular canals
Crus ampullare-crista ampullaris
Utricle&Saccule-maculae acousticae
Statoacoustic ganglion CN VIII

15. Development of the semicircular canals
Note:disappearance of the central portion & the ampullae in the semicircular canals

16. Development of the Middle Ear
Expansion of 1st pharyngeal pouch middle cavity & auditory tube
**Lining- endodermal origin**
2nd mo.-blind end oftubotympanic tube st pharyngeal cleft

17. Development of the middle ear
Note:tubotympanic recess, mesenchymal condensation ear ossicle formation

18. 6thwk.-condensation of mesenchyme (mesoderm):just dorsal to the end of tubotympanic end ear ossicles
Tympanic cavity-ear ossicles in loose mesenchyme late pregnancy: programmed cell death suspension of ear ossicles
2 mo. after birth-free movement of ear ossicles

19. Development of the ear ossicles in the tympanic cavity
Note: malleus contact with eardrum, stapes contact with oval window and endodermal epithelium of tympanic cavity

20. Dual origin of ear ossicles
malleus & incus-mesoderm of 1st branchial arch
stapes-mesoderm of 2nd branchial arch
*Tensor tympani mus.- CN V
*Stapedius - CN VII

21. Development of the External Ear
Pinna - mesenchyme of 1st &2nd branchial arches:2nd mo. auricular hillock enlargement(asymmetry)
External auditory meatus - inward expansion of the 1st branchial cleft
3rd-meatal plug(solid epith. plate)
7th-dissolution of meatal plug

22. Lateral view of the head showing the six auricular hillocks surrounding the dorsal end of the 1st pharyngeal cleft

23. Congenital malformation of the ear
Congenital deafness-inner ear deafness(rubella),middle ear deafness (1st & 2nd arches),agenesis of external ear
Auricular anomalies

24. THE END