3. Kural 411
செல்வத்துட் செல்வஞ் செவிச்செல்வம் அச்செல்வம்
செல்வத்து செல்லாந் தலல.
TRANSLATION
Wealth of wealth is wealth acquired be ear attent;
Wealth mid all wealth supremely excellent.
EXPLANATION :
Wealth (gained) by the ear is wealth of
wealth; that wealth is
the chief of all wealth.
5. Inner ear
• It exits within the temporal bone (
petrous bone )
• It is a complex structure . It is located
in a bony cavity called bony labyrinth
• It is filled with a fluid called perilymh ,
which is similar to CSF
8. Membraneous labyrinth
• Has 2 parts
• semicircular canal – 3 lateral ,
posterior & superior ( crista ampularis )
angular secretion
• utricle & saccule – utricle 5 opening of
semicircular canal ( macula ) linear
acceleration
9. cochlea
• central axis modiolus
• cochlear canal – runs 2 ½ turns
• cochlear duct - Scala vestibule , Scala
tympani , Scala media & organ of corti
openings – fenestra vestibule
& fenestra cochlea
hair cells ( inner & outer )
transduction of mechanical
energy to electrical energy
10.
11. • cochlear canal - divided into Scala
vestibuli & Scala tympani by spiral
lamina & basilar membrane
cochlear duct is within
cochlear canal
receptor of organ hearing –
organ of corti
• organ of corti - specialized organ of
hearing
lies within cochlear duct
on the basilar membrane
contains hair cells –
impulses carried by VII nerve
12.
13. • receptors for balancing – macula (
thickening – in the walls of saccule &
utricle )
crest ( in the
ampulla of semicircular ducts )
14. Basilar membrane
• Forms the floor of scala media
• 35mm long
• Auditory nerve endings are located
in BM
• Organ of corti resides on the BM
15.
16. • Width
• Base ( 0.1 mm ) = narrow & stiff
• Apex (0.5 mm ) = boad / wide &
flaccid
• Opposite to cochlear ducts width
• Reacts more to vibrations of IE than
do most of the other structures.
17. Hair cells
• Hair cells lays down on the fibrous BM
• 3 – 5 rows of 12, 000 o 15, 000 parallel
outer hair cells (OHCs)
• One row of 3, 000 inner hair cells ( IHCs)
• On the top of each hair cells are hair –
like projection called “stereocilia”
• Stereo cilia on the top of OHCs are
embedded in the tectorial membrane
18.
19. The direction in which stereo cilia are
bent during stimulation
• If cilia bend in one direction – nerve
cells are stimulated
• If cilia bend in the other way – nerve
impulses are inhabited
• If cilia bend to the side - no
stimulation at all
20. cochlear microphone
• Resemblance between cochlea &
microphone in their function
• cochlea convers sound waves into an
energy form useful to the auditory nerve
• microphone converts the sound pressure
coming form a speakers mouth into an
alternating electrical current
• This action is called cochlear
microphone (CM )
21. • a result of changes in polarization caused
by the bending back & forth of hair cells
cilia
• for every up & down cycle of BM , there is
an one in & out cycle of stereo cilia of the
OHCs causing them to become
alternatively depolarized & hyper
polarized
• CM can be measured by placing needle
electrode over the RW or within the
cochlea
22.
23. Action potential
• A change in the electrical potential
occurring on the surface of each
neuron after they are being stimulated
by HCs
• Increases in the intensity of the
auditory input signal to the cochlea
result in increased electrical output
from HCs
• This stimulation causes increased
electrical activity in the neuron
24. Transformer action
• It is accomplished by
• Lever action of ossicles : handle of malleus is 13
times longer than long process of incus
25. Hydraulic action of
tympanic membrane
• the area of tympanic membrane is much
larger than the area of stapes footplate . the
average ration is 21:1 .
• the effective vibratory area of tympanic
membrane is only 2/3 rd. , so the effective
area ratio is reduced to 14: 1 .
• this is the mechanical advantage provided by
the tympanic membrane
27. CLINICAL ANATOMY OF INNER
EAR
1. Benign paroxysmal positional vertigo (BPPV)
- also known
as positional vertigo
- It is a dizzy or spinning
sensation in your head
- most common type
of vertigo.
28. 2. Meniere's disease
causes episodes of vertigo, ringing
in the ears (tinnitus), ear
pressure/fullness and hearing loss.
29. 3. Labyrinthitis and vestibular
neuritis
- occurs when the
Hearing & balance
nerves become inflamed
- resulting in sudden
1. hearing loss
2. balance problems
3. vertigo.
30. 4. Superior semicircular canal dehiscence (SSCD)
- patient has a loss or absence
of the bone that covers
your superior
semicircular canal
Symptoms
1. pressure/
sound-induced vertigo
2. hearing loss
3. ear pressure,
4. hearing your
own breathing and blinking
31. REFERENCES
• Diseases of Ear, Nose and Throat & Head
and Neck Surgery by P L Dhingra
• BD Chaurasia's Human Anatomy Regional
and Applied Dissection and Clinical: Vol. 3:
Head-Neck Brain