The ear is divided into three parts: the outer, middle, and inner ear. The outer ear collects sound waves and directs them through the external auditory canal to the eardrum. The middle ear contains three small bones (ossicles) that amplify vibrations through bone conduction to the inner ear. The inner ear converts vibrations into neural signals for hearing and balance via the cochlea and semicircular canals. Sound waves are transduced into mechanical, then hydraulic, then electrical energy as they travel through the ear to be interpreted by the brain.

1. By –
Mr. ASHOK BISHNOI
Lecturer, JINR

3. ANATOMY AND
PHYSIOLOGY OF THE
EAR

4. Divided into “3” parts:-
1. Outer Ear
2. Middle Ear (Tympanic cavity)
3. Inner Ear

5. Major Divisions of the Ear
Peripheral Mechanism Central Mechanism
Outer
Ear
Middle
Ear
Inner
Ear
VIII
Cranial
Nerve
Brain

8.  It consist of the auricle (Pinna) & External
acoustic meatus ( Auditory canal)

9. Pinna Landmarks
 Helix
 Antihelix
 Concha
 Tragus
 Intertragal Notch
 Antitragus

10. 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

11. 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)

12. 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

13. 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

14.  Collect sound
 Localization
 Resonator
 Protection
 Sensitive (earlobe)

15. This is irregular shaped air filled
cavity.
1- Malleus
2- Incus
3- Stapes
6- Eustachian Tube

16. 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

17. 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.

19.  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

20.  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. 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. 23
Organ of Corti
 The end organ of hearing;
contains stereocilia and
hair cells.

24.  Convert mechanical sound
waves to neural impulses that
can be recognized by the
brain for:
 Hearing
 Balance

25. 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

26. Flow of ear:-

27.  Hearing
 Sound Conduction and Transmission
 Balance and Equilibrium