INNER EAR AND A DESCRIPTION ABOUT ANATOMY AND PHYSIOLOGY OF INNER EAR

1. AR
E
ER Y HOM
NN B T
I
N
TI
NI
DR
AS
I nininni

2. INNER EAR
 DEVELOPMENT
OF INNER EAR
Begins : 3rd week of fetal life
Completes : 16th week
Membraneous & Bony labyrinth
develop from otic capsule
Ectoderm in hind brain
Auditory Placode
Auditory vesicle
differentiates
- Endolymphatic duct &
- sac

3. Semicircular ducts
Utricle
Saccule
Cochlea
Pars
Superior
Pars
Inferior

5. INNER EAR / LABYBRINTH
BONY & MEMBRANOUS LABYRINTH
ENDOLYMPH
BONY
LABYRINTH
VESTIBULE
SEMI CIRCULAR
CANALS
COCHLEA
seperated by PERILYMPH

7. Vestibular
apparatus for
balance and equilibrium
Cochlea for
hearing

9. A} VESTIBULE
Central chamber
Lateral wall : oval window
Spherical- lodges saccule
Medial wall : 2 Recessess
Elliptical- lodges utricle
Spherical R. – has perforated holes
Maculae Cribrosa Media –
inferior vestibular nerve
Elliptical R. –
Maculae Cribrosa Superior (Mike’s spot)
– “Translabyrinthe” approach
N to Utricle & ampulla

11. B} SEMI CIRCULAR CANALS
Lie At
to each other
Rt
Superior
(15-20mm)
Angles
lateral
(12-15mm)
Posterior
(18-20mm)
lie
lie
transverse
to petrous part of
Temporal bone
Parallel to petrous part of
temporal bone
bulge into aditus & antrum

12. Ampullated end-opens into vestibule
Non Ampullated end of Supr & Post’r canals
Unite – common channel –
CRUS COMMUNE(4MM)
C}
COCHLEA
Snail
Lies Antr to bony labyrinth
L=30mm
Coiled tube
2.5 - 2.75 turns around central pyramid of bone
MODILOUS – spirally –OSSEOUS SPIRAL
LAMINA

13. base towards Int. Acoustic Meatus
transmits cochlear vessels & nerves
•
Bony cochlea : 3
compartments
Scala Vestibuli
Scala Tympani
Scala media
(Membranous cochlea)
-
perilymph
- communicate via cochlea apex
HELICOTREMA
Endolymph

19. MEMBRANOUS
LABYRINTH
Consists “ESCUSE”
-Endolymphatic duct
-Semi circular duct
-Cochlear duct
-Utricle
-Saccule
-Endolymphatic sac
COCHLEAR DUCT / MEMBRANOUS COCHLEA /
SCALA MEDIA
• Coiled tube
• Triangular on cross section
• 3 walls :

21. Basilar memb
– supports organ of corti - has sound receptors
- thin inner part ZONA ARCUATA
- thick outer part ZONA PECTINATA
- seperates Scala tympani from scala media
-its length from Basal coil (High freq sound) – Apical coil (low freq
sound)
Reissner’s membrane
Seperates scala vestibuli - scala media
Stria vascularis
-Vascular epith.
-Endolymph secretion
Cochlear duct connects to saccule by DUCTUS REUNIENS

22. Organ
of
corti
• Spead entirely over Basilar memb
Has TUNNEL OF CORTI – consists of 2 rows of rods of inner & outer hair
cells
1 row of inner hair cells & 3-4 rows of outer hair cells
Inner rods-3500
Outer rods-12000
Hair cells supported by Pillar cells , Dieter cells , Hensens cells

Mechanical sound energy gets
transduced into electrochemical
energy

23. TECTORIAL MEMBRANE
• Has gelatinous matrix with fibers
• Lies above Organ of corti
• Its undersurface attaches to tip of outer hair cells
Shearing force b/w them stimulates hair cells

24. UTRICLE & SACCULE
Both lie in bony vestibule but saccule lies anterior to utricle
Utricule connects to saccule via
UTRICOSACCULAR DUCT
Cochlear duct connects to saccule via DUCTUS REUNIENS
Utricle has 5 openings of 3 semicircular canals
Spherical recess-Saccule (S-S)
Elleptical recess-Utricle
U – lies horizontally
Its vestibular receptor organ MACULA
S- lies vertically
Linear acceleration & decelaration
Has hair cells + supporting cells + gelatinous mass
secreted by
has
Mucopolysaccharides

25. Gelatinous mass – also contains – CaCO3 crystals
OTOLITH / STATACONIA

26. ENDOLYMPHATIC DUCT & SAC
• Union of 2 ducts (1 from saccule and 1 from utricle)
• Pass through Vestibular Aqueduct
• Terminal end – dilated – forms ENDOLYMPHATIC SAC

28. SEMICIRCULAR DUCTS
3 in number
Open in utricle
Ampullated end – has thick neuroepithelium – CRISTA AMPULLARIS
Hair cells + Supporting cells + Gelatinous mass
dome shaped In cristae
CUPULA

30. HAIR CELLS
2 types
type 1
(FLASK SHAPED)
Summit
Hair cells
type 2
(CYLINDRICAL)
CRISTAE
1 KINOCILIUM
Periphery
Many STEREOCILIA (60-110)

31. Inner hair cells – Afferent Cochlear fibers – transmit auditory impulses
Outer hair cells – Efferent fibers – modulate inner hair cells fx
Supporting cells
Dieters cell - lie in b/w outer hair cells
Outside it - Hensens cells lie

32. MECHANISM
OF
HEARING
TM
SOUND
PINNA
AUDITORY N.
EAC
Vibration of
TRANSDUCTION
Pr. Changes in
OSSICULAR CHAIN
FOOT PLATE
OF STAPES
LABYRINTHINE
FLUID
STIMULATES HAIR CELLS OF
BASILAR MEMB.MOVES
ORGAN OF CORTI
COCHLEAR NUCLEI - SUPR. OLIVARY COMPLEX – LAT. LEMNISCUS – INFR. COLLICULUS
AUDITORY CORTEX
(AREA 41 / BROADMANN’S AREA)
MEDIAL GENICULATE BODY

33. BLOOD
SUPPLY
LABYRINTHINE @ {Br. Of Antr Infr Cerebellar @}
common cochlear
Antr Vestibular @
{Utricle , Supr & Lateral
Canal}
Vestibulo cochlear
Cochlear br.
{ 20% Cochlea}
Main cochlear
{ 80% Cochlea}
Postr Vestibular @
{Saccule ; Postr Canal}