Anatomy of ear for undergraduate students ( MBBS ) . Basic anatomy of ear with its clinical importance nerve supply of ear blood supply of ear middle ear ossicles malleus incus stapes muscles of middle ear mastoid air cells pinna tympanic membrane lymphatics of ear walls of middle ear organ of corti middle ear cleft facial recess sinus tympani chorda tympani embryology of ear

1. ANATOMY OF EAR
- Dr. Alka Kapil
( Assistant Professor,
Dept. of ENT & HNS, MKCG Medical

2. The EAR is comprised of three parts :
External ear Middle ear Inner ear
Pinna,EAC,TM

3. Pinna
 Single elastic fibrocartilage
 Cartilaginous landmark for
mastoid antrum
 Skin on lateral aspect is tightly
adherent to underlying
perichondrium
Perichondritis, furuncle
 Tragal & conchal cartilage
plastic reconstruction
Incisura terminalis

4. External auditory canal
 24 mm = 8mm ( cartilaginous)+ 16mm ( bony)
 Isthmus = 6mm lateral to Tympanic membrane
Foreign body lodgement
 Anterior recess
 Fissures of Santorini
 Foramen of Huschke
 Skin over outer cartilaginous part has hair follicles, inner
one devoid of them
Furunculosis

5. Tympanic Membrane
• Forms a partition between EAC & Middle ear
• Located at the medial end of EAC and forms the
lateral wall of tympanic cavity
• Pearly white/ grey in colour
• Oval in shape
• Dimensions : 9-10 mm X 8-9mm X 0.1 mm
• Surface area – 90 mm2 ; effective area – 45mm2
• Forms an angle of 55 0 with the floor of EAC

6. • Pars tensa and pars flaccida
• Epithelial, fibrous & mucosal layers
• Tympanic annulus
• CONE OF LIGHT : Anteroinferior quadrant
(R5 L7 o’clock)
• Anterior malleolar fold and posterior
malleolar fold
• Notch of Rivinus

7. Nerve supply of ear
Pinna A) lateral surface B) medial surface EAC and lateral surface of tympanic membrane
Medial surface of tympanic membrane:
JACOBSON’S NERVE (IX)
Clinical implication : Referred Otalgia, Hitzelberger’s sign, Ramsay Hunt syndrome

8. Lymphatic drainage of ear

9. Middle ear cleft & middle ear
The middle ear together with eustachian tube, aditus ad
antrum and mastoid air cells is called middle ear cleft

10. Tympanic cavity : walls & content

12. Diagramatic representation of tympanic cavity, its walls and content

13. Middle ear ossicles
(SADDLE)
(BALL & SOCKET)

15. Muscles of Middle ear
 Tensor tympani
 Stapedius

16. Chorda tympani nerve
 Branch of Facial nerve which enters the middle ear
through posterior canaliculus
 Runs on medial surface of TM between handle of malleus
& long process of incus
 Leaves by anterior canaliculus to join petrotympanic
fissure
 Carries taste sensation from anterior 2/3rd of of the same
side of tongue

17. Mastoid and its air cell system
• Mastoid is the part of temporal bone which lie
posterior to the middle ear cavity
• Comprising of three parts :
1.Aditus ad antrum
2.Mastoid antrum – largest and most prominant
mastoid air cell
3.Mastoid air cell

18. Mac Evan’s triangle
Landmark for mastoid antrum during MASTOIDECTOMY surgery

19. Sinus Tympani
 Lies medial to the facial nerve
 Boundaries :
L - Facial nerve
M - PSCC
S - Ponticulus
I - Subiculum
 Clinical importance : MC site for residual cholesteatoma

20. Facial recess
 Lateral to the facial nerve
 Boundaries :
M - Facial nerve
L - Annulus
S - Short process of incus
I - Chordofacial angle
 Clinical importance – posterior tympanotomy for
cochlear implant
Chordofacial angle

21. Inner ear
• Bony labyrinth : comprises
Vestibule
Semicircular canals (SCC)
Cochlea
• Membranous labyrinth : comprises
(It contains endolymph and all of the neuroepithelia required for hearing and balance)
Utricle & Saccule
Cochlear duct
SCC duct
Endolymphatic sac & duct

23. Cochlea
 Divided into Scala vestibuli
Scala media
Scala tympani
 Scala media is filled with endolymph
 Scala vestibuli & scala tympani filled with
perilymph
 Houses the organ of corti in its scala media
Clinical implication: MENINGITIS

24. Organ of corti
 Receptor organ for hearing
 Located at the basilar membrane of the scala media of
cochlea
 Comprise of : HAIR CELLS
TECTORIAL MEMBRANE
TUNNEL OF CORTI
SUPPORTING CELLS

25. Movement of stapes footplate
(transmitted to cochlear fluid)
Move the basilar membrane
Shearing force between tectorial plate and
hair cells
Distortion in the hair cells generate cochlear
impulse

27. Blood supply of inner ear

28. Embryology of ear
1st & 2nd branchial arch give rise to 6
mesodermal tubercles ( Hillocks of His )
fuses to form PINNA
TRAGUS & ascending limb of helix - 1st
branchial arch
Rest of pinna – 2nd branchial arch
1st branchial cleft
Meatal plug
Recanalization of meatal plug
from medial to lateral
direction
EAC
Middle ear cleft
Membranous
labyrinth
TYMPANIC MEMBRANE - all 3 germ layers
Surface neuroectoderm
Bony
labyrinth
mesoderm