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By –
Mr. ASHOK BISHNOI
Lecturer, JINR
ANATOMY AND
PHYSIOLOGY OF THE
EAR
Divided into “3” parts:-
1. Outer Ear
2. Middle Ear (Tympanic cavity)
3. Inner Ear
Major Divisions of the Ear
Peripheral Mechanism Central Mechanism
Outer
Ear
Middle
Ear
Inner
Ear
VIII
Cranial
Nerve
Brain
 It consist of the auricle (Pinna) & External
acoustic meatus ( Auditory canal)
Pinna Landmarks
 Helix
 Antihelix
 Concha
 Tragus
 Intertragal Notch
 Antitragus
Auricle (Pinna):-
 It is visible part of ear
 It composed of fibro elastic cartilage
convered with skin.
 Helix- it is outer ridge part
 Lobule (Ear lobe) –Soft pliable part
External acoustic meatus ( Auditory
canal)
 Slightly “S” Shaped tube
 About 2.5 cm long ( 1 inch )
 External from auricle to tympanic
membrane
 There numerous ceruminous gland &
hair follicles
 Numerous gland are modified sweat
gland that secret cerumen (Earwax)
Tympanic membrane (Eardrum):-
 Thin membrane
 It is Oval shaped
 Forms boundary between
outer and middle ear
 Vibrates in response to
sound waves
 Changes acoustical
energy into mechanical
Mastoid Process of
Temporal Bone
 Bony ridge behind the auricle.
 Hardest bone in body,
protects cochlea and vestibular
system.
 Provides support to the
external ear and posterior wall
of the middle ear cavity.
 Contains air cavities which can
be reservoir for infection
 Collect sound
 Localization
 Resonator
 Protection
 Sensitive (earlobe)
This is irregular shaped air filled
cavity.
1- Malleus
2- Incus
3- Stapes
6- Eustachian Tube
The Ossicles
 Ossicular chain = malleus, incus &
stapes
 Malleus (It is Hammer shaped bone)
 TM attaches
 Incus (It is Anvil shaped bone)
 Connector function
 Stapes ( It is a Stirrup shaped bone)
 Smallest bone in the body
 Footplate inserts in oval window on
medial wall
Focus/amplify vibration of TM to smaller
area, enables vibration of cochlear
fluids
Eustachian Tube (Pharyngotympanic
tube) ( “The Equalizer”)
 Mucous-lined, connects middle ear
cavity to nasopharynx
 “Equalizes” air pressure in middle ear
 Normally closed, opens under certain
conditions
 Closing of the Eustachian tube
protects the middle ear from
unwanted pressure fluctuations and
loud sounds.
 Conduction
 Conduct sound from the outer ear to the inner ear
 Protection
 Creates a barrier that protects the middle and inner areas
from foreign objects
 Transducer
 Converts acoustic energy to mechanical energy
 Converts mechanical energy to hydraulic energy
 Amplifier
 Transformer action of the middle ear
 The inner ear contain the organ of hearing &
balance
 It consist of –
 Vestibule (Balance)
 Cochlea
 Semicircular canal
Cochlea - Snail-shaped organ with a series of fluid-filled
tunnels; converts mechanical energy into
electrical energy
22
Oval Window – located at the footplate
of the stapes; when the footplate vibrates,
the cochlear fluid is set into motion
Round Window – functions as the pressure
relief port for the fluid set into motion initially by
the movement of the stapes in the oval window
23
Organ of Corti
 The end organ of hearing;
contains stereocilia and
hair cells.
 Convert mechanical sound
waves to neural impulses that
can be recognized by the
brain for:
 Hearing
 Balance
Pathway of Sound:-
 Sound waves enter pinna travel through auditory canal
 Sound waves strike tympanic membrane causing vibrations
(mechanical energy)
 Vibrating TM causes ossicles to vibrate
 Vibrating stapes bone at oval window generates movement of
cochlear fluid (Hydralics)
 Fluid movement stimulates cilia- lined cochlea
 Cilia sends electrical impulses along auditory nerve to brain
for interpretation
Flow of ear:-
 Hearing
 Sound Conduction and Transmission
 Balance and Equilibrium