complete coverage of embryology of ear. and it is authentic.

1. EMBRYOLOGY
OF THE EAR
Dr Zeeshan Ahmad
M.S.(ENT,PGY1)
Nalanda Medical College & Hospital,
Patna

2. Introduction
• The ear comprises three distinct parts.
– External ear
– Middle ear
– Internal ear
• Each part embryologically different.

3. INTERNAL EAR
• First seen at 22 weeks as Otic Placodes.
• Invaginate forming Otic Vesicle.
• Otic Vesicle divides
– Dorsal Utricle, SSC, endolymphatic duct
– Ventral Saccule, Cochlear duct
22 days
4 weeks

4. • In the 6th week saccule forms
– Ventral  tubular outpocketing at its
lower pole  COCHLEA
• Cochlea penetrates
mesenchyme 2.5 turns in
spiral manner by 8 weeks.

5. • Mesenchyme surrounding cochlear duct
differentiates into cartilage shell.
• At 10th week undergoes vacuolization
– Scala Tympani (Basilar memb.)
– Scala Vestibuli (Vestibular memb.)
– Modiolus (medial)
– Spiral ligament (lat)

7. ORGAN OF CORTI
• Epithelial cells of cochlear duct
– Inner ridge forms Spiral Limbus
– Outer ridge
• One inner hair cells
• Four outer hair cells
• Covered by Tectorial membrane attached
to spiral limbus

8. – Dorsal  • In the 6th week utricle forms
flattened outpocketings
• Central portions appose and
then disappear  SSC
• One end widens  ampulla

9. • During formation of the otic vesicle, a
small group of cells breaks away from its
wall and forms the statoacoustic ganglion.
• Also recieves cells from Neural Crest.
• Splits into cochlear & vestibular parts and
supplies Organ of Corti and the vestibular
apparatus respectively.

10. MIDDLE EAR
• Tympanic cavity
• Auditory tube
• Ossicles

11. • Beginning at week 4, the tubotympanic
sulcus develops as an extension of the
endodermal epithelium of the first
pharyngeal pouch
• Distal part  primitive tympanic cavity
• Proximal part Auditory tube (eustachian
tube)

12. • The expanding end of the tubotympanic
sulcus comes into proximity with the
medial aspect of the ectodermal first
pharyngeal cleft, the primordial external
auditory canal.
• Distal part  primitive tympanic cavity
• Proximal part Auditory tube (eustachian
tube)

13. MASTOID
• Growth of the tympanic cavity into the
mastoid portion of the temporal bone 
Mastoid antrum
• The attachment of the sternocleidomastoid
on the temporal bone Mastoid process.
• Although the development of the mastoid
air cells begins in fetal life, full maturation
does not occur until age 2.

14. OSSICLES
• Beginning sometime between weeks 4
and 7, a condensation of neural crest
ectoderm embedded within the
mesenchyme begins to form the ossicles
BROADLY speaking--------
• Malleus and Incus  first pharyngeal arch
• Stapes  second arch

15. • Meckel’s cartilage, which is derived from
the first pharyngeal arch
– Head of Malleus
– Body of Incus
• Reichert cartilage, which is derived from
second arch
– Manubrium of Malleus
– long process of Incus
– Suprastructure of Stapes

16. • Development of the stapes footplate is
induced by a depression on the otic
capsule, the lamina stapedialis.
• This occurs between weeks 6 and 9.

17. • Although the ossicles appear during the
first half of fetal life, they remain
embedded in mesenchyme until the eighth
month , when the surrounding tissue
dissolves.

18. • When the ossicles are entirely free of
surrounding mesenchyme, the
endodermal epithelium connects them in a
mesentery-like fashion to the wall of the
cavity
• The supporting ligaments of the ossicles
develop later within these mesenteries.

19. EXTERNAL EAR
• Auricle
• External Auditory Meatus
• Tympanic Membrane

20. AURICLE
• The auricle
develops from six
mesenchymal
proliferations at the
dorsal ends of the
first and second
pharyngeal arches,
surrounding the first
pharyngeal cleft.

21. AURICLE
• These swellings
(auricular
hillocks), three
on each side of
the external
meatus, later
fuse and form
the definitive
auricle.

22. AURICLE
• These swellings
(auricular
hillocks), three
on each side of
the external
meatus, later
fuse and form
the definitive
auricle.

23. • Initially, the external ears are in the lower
neck region but with development of the
mandible, they ascend to the side of the
head at the level of the eyes.

24. External Auditory Meatus
• The external auditory meatus develops
from the dorsal portion of the first
pharyngeal cleft.
• At the beginning of the third month,
epithelial cells at the bottom of the meatus
proliferate, forming a solid epithelial plate,
the meatal plug.

25. • In the seventh month, this plug dissolves,
and the epithelial lining of the floor of the
meatus forms the definitive eardrum.
• At the beginning of the third month,
epithelial cells at the bottom of the meatus
proliferate, forming a solid epithelial plate,
the meatal plug.

26. TYMPANIC MEMBRANE
• The eardrum is made up of
epithelial lining at the bottom of
the auditory meatus,
– endodermal epithelial lining of the tympanic
cavity, and
– intermediate layer
of connective tissue.

27. Derangement of development
• There an exhausting list of disorders.
• lets name a few.
– Treacher collins
– Pendred
– Crouzon
– Preauricular sinus

28. Treacher Collins
– Atresia of external
auditory canal
– malformed auricle
– Middle and inner ear
anomalies
– Downward slanting eyes
– Micrognathia
– Underdeveloped zygoma.
– Drooping of part of the
lateral lower eyelids

29. Pendred Syndrome
– Sensorineural deafness
– Widened vestibular aqueduct
– Shortened cochlea

30. Crouzon’s disease
– Atresia of external auditory
canal
– Malformation of ossicles
– Fusion of different sutures
leads to different patterns
of growth of the skull.

31. Congenital Preauricular Sinus
Failure of fusion of first and second arch
tubercles

32. THANK YOU