inner ear anatomy or under gradu

1. ANATOMY OF INNER EAR
Dr. S. NAGA RAJU
M.S.(ENT)
VISWABHARATHI MEDICAL COLLEGE
KURNOOL
27-03-2019

2. • Inner ear concerned
with hearing and
balance
• Consists of :
a) Bony Labyrinth
b) Membranous
Labyrinth

3. BONY LABYRINTH
• Consists of :
a) Vestibule
b) Semicircular
Canals
c) Cochlea

4. Vestibule
• Central part of bony
labyrinth
• Lies b/w the medial wall
of the middle ear and
lateral to the IAM
• Posteriorly –SCC
• Anteriorly- COCHLEA
• Superiorly- DURA
• Inferiorly- Petrous part
of the temporal bone

5. • Bean shaped opening present over the lateral
surface of the bony vestibule called as oval window
which is occupied by the foot plate of stapes
surrounded by annular ligament.
• Medial wall- anterior part has spherical recess which
lodges saccule
• Posterior part has elliptical recess which lodges
utricle
• Ant and post seperated by vestibular crest

6. Semi circular canals
• SUPERIOR SCC-(15-
20mm) present transverse
to the bony axis of petrous
part of the temporal bone
• Anterio lateral part of
sscc is ampulated and
opens in the upper lateral
part of the vestibule
• Non amupated part fuses
with superior limb of post
scc forms CRUS
COMMUNE

7. • POST SCC-(18-22mm)-
paralell to the post
surface of the petrous
part of the temporal
bone
• Superior non ampulated
part fuses with lower
end of the sscc forms
crus commune
• Lower ampulated part
opens into the lower
part of the vestibule

8. • LATERAL SCC(12-
15mm) projected as
rounded bulge into
aditus and antrum of
middle ear cleft
• Lies 30 degree angle to
the horizontal plane
• Upper ampulated part
opens in upper part of
vestibule lower part just
below the crus-
commune opening

9. BONY COCHLEA
its resembles like snail
It’s a hollow tube having
2 and ¾ of the turn
around bony central
axis called
MODIOLUS
With in the bony canal
membranous
cochelar duct present

10. • Scala vestibuli
• Scala media
• Scala tympani
• S.vestibuli and scal
tympani communicates
in apex of the cochelar
duct called helicotrama
• Osseous spiral lamina
turn around the
modiolus and perates
s.media and s.tympani

11. Membranous labyrinth
• Membranous vestibular
labyrinth
• Membranous
semicircular ducts
• Membranous cochlear
labyrinth

12. LABYRINTH

13. Membranous vestibular
labyrinth
• 1.Saccule
• 2.Utricle
• 3. Endo lymphatic
duct and sac

14. Saccule
• Saccule present anterior to the utricle opposite to
the foot plate of stapes
• Saccule present in the spherical recess in the bony
vestibule
• Saccule and utricle connected with utriculosaccular
duct
• saccule is connected with cochlear labyrinth called
membranous cochlear reuniens
• It has sensory epithelium called macula vertically
placed over the saccule responds to the linear
acceleration and deceleration

15. Utricle
• Utricle les in the post surface of the bony vestibule
• It receives five openings of 3 scc
• It connects with saccule utriculo saccular duct or
indirectly with endolymphatic duct
• Sensory epithelium in utricle is called Macula and
horizontally placed in utricle
• Conserned with linera acceleration and deceleration

16. Endolymphatic duct and
sac
• Formed by two ducts
one from saccule and
another from utricle
• Passes through
vestibular aqueduct
• Terminal part dilated
and form SAC
• Lies b/w two layers of
the dura
•

17. VESTIBULAR RECEPTOR ORGANS
o The vestibular receptor organs of saccule and utricle are
called macula.
o Macula of saccule lies vertically in its medial surface
whereas in utricle it lies horizontally
o These receptor organs are composed of hair
cells,supporting cells and gelatinous mass
o This gelatinous mass is composed of
mucopolysaccharides ,secreted by the supporting cells
o Macular gelatinous mass contain additional materials
madeup of caco3 crystals known as otolith or
statoconia.hence this gelatinous mass is sometimes
called statoconial membrane.

18. 20-07-2012www.nayyarENT.com

19. VESTIBULAR SENSORY
CELLS
TYPE I CELLS:
• Flask shaped
• Surrounded by nerve
chalice
• Collateral extensions on
Type II cells
TYPE II CELLS:
• Synapse with the
collaterals & with the
membranes of the
chalices
• Cylindrical

20. 20-07-2012www.nayyarENT.com

21. MEMBRANOUS
SEMICIRCULAR DUCTS
 These ducts lie in the bony semicircular canals.
 One end of each semicircular duct gets dilated
before entering the utricle.
 The dilated part is filled in the ampullary end of the
bony semicircular canal. It accomodates the
specialised vestibular epithelium known as
cristae.
 This cristae also has hair cells , supporting
cells,gelatinous mass.
 This gelatinous mass in cristae is dome shaped
hence called cupula.

22. 20-07-2012www.nayyarENT.com

23. (COCHLEAR DUCT/SCALA
MEDIA)
 It occupies the midportion
of cochlear canal and is
triangular in cross
section.
 Floor is formed by the
basilar membrane ,roof by
reissners membrane
,lateral wall by stria
vasularis and bony wall of
cochlea.
 Stria vascularis is thought
to play an active role in
maintenance of ionic
composition and
electrical potential of
endolymph.

24.  Basilar membrane supports organ of corti ,
containing the sound receptors.
 Organ of corti is spread like ribbon along the entire
basilar membrane.
 The thin area of basilar membrane in its inner part is
called zona arcuata , thicker outer part is zona
pectinata.

25. ORGAN OF CORTI
 It is sense organ of
hearing, set upon the
basilar membrane.
 It consists of sensory
cells with
hairs,supporting cells and
gelatinous membrane.
 The hair cells are
disposed in a single row
of inner haircells , 3 or 4
rows of outer hair cells
and supported externally
by cells of hensen.

26. 20-07-2012www.nayyarENT.com

27.  Nearly 17000 haircells ,
4500 inner, 12500 outer
rows.
 The space between the
pillars is tunnel of corti ,
which contains
cortilymph.
 The inner hair cells are
bullous in shape
resembling type 1 cells of
vestibular labyrinth and
outer hair cells are
columnar like type2
vestibular cells.

28. CELLULAR ARCHITECHTURE AND
FUNCTION OF ORGAN OF CORTI
• Sensory region consists
of 2 types of sensory hair
cells with apical
stereocilia
• Stereocilia project into
the overlying endolymph
• Inner hair cells form a
single row while outer
hair cells form 3-4 rows
• Separated by 2 rows of
pillar cells from the
Tunnel of Corti

29. SCALA VESTIBULI &
SCALA TYMPANI
• Scalamedia ends as blindsac
& separates cochlear bony
canal into 2 passages.
• The upper chamber of
perilymph is scalavestibuli ,
closed by stapes footplate,
communicates functionally
with middle ear through oval
window.
• The lower one is scalatympani
, closed by secondary
tympani membrane,
communicates functionally
with middleear through round
window.
• .

30. • These 2 chambers
communicate with one
another at the apex of
the modiolus through
helicotrema.
• Scalatympani also in
connection with
subarachnoid space by
way of cochlear
aqueduct in cochlear
canaliculus.

32. Inner ear fluids
Perilymph Endolymph
• Resembles extracellular
fluid
• Rich in sodium ion
• Comminicates with csf
through aqueduct of
cochlea
• Perilymph formed by
• 1.blood filterate from
capillaries of spiral
ligament
• 2. direct continuation of
csf
• Intra cellular fluid
• Rich in potassium ions
• Secretory cells of strai
vascularies of cochlea
• Longitudinal flow-
cochlea-utricle&saccule-
endolymphatic sac-
subdural space
• radial flow- strai
vasularies- get absorbed
by strai vascualries

33. VASCULAR SUPPLY OF LABYRINTH

34. Venous drinage
• Vein of internal auditory
vein
• Vein of vestibular
aqueduct
• Vein of cochelar
aqueduct
• Drains into inf petrosal
sinus-lateral venous
sinus

35. MEMBRANOUS
LABYRINTH
Dr Rajesh
PG in ENT
23-11-2013.