Ppt

1. 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. Ventral cochlear region
Saccule Cochlear duct
Utricle Semicircular
canals
Endolymphatic
duct
Membranous labyrinth

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
Scala media
Cartilageous shell
Scala vestibuli Scala tympani
Vestibular mem.
Basilar mem.
Organ of Corti
(S.media & S.vestibuli)

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
3 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 1st 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