AUDITORY OSSICLES MALLUS INCUS STAPES WORKING OF AUDITORY OSSICLES

1. In the name of Allah, the Entirely Merciful, the
Especially Merciful.
1

2. BONES OF EAR

3. AUDITORY OSSICLES:
• Auditory ossicles are a chain of small bones in the middle ear that
transmit sound from the outer ear to the inner ear through mechanical
vibration.
 NAMES of the bones that comprises the auditory ossicles are,
1. The Malleus (hammer)
2. The Incus (anvil)
3. The Stapes (stirrup)

4. THE MALLEUS
 Malleus is the largest ossicle that possesses,
1. Head
2. Neck
3. Handle
4. Process(anterior and posterior)
 HEAD: Rounded and articulates posteriorly with the incus.
 NECK: Constricted part below the head.
 HANDLE: Passes downward and backward and is attached to the medial surface of the
tympanic membrane.
 ANTERIOR PROCESS: is a spicule(sharp pointed object) of bone that is connected to
the anterior wall of the tympanic cavity by a ligament.
 LATERAL PROCESS: projects laterally and is attached to the anterior and posterior

5. THE INCUS
 The INCUS possesses
1. Large body
2. Two processes(short & long).
 BODY: is rounded and articulates anteriorly with the head of the
malleus.
 LONG PROCESS: descends behind and parallel to the handle of the
malleus. Its lower end bends medially and articulates with the head of the
stapes.
 SHORT PROCESS: projects backward and is attached to the posterior
wall of the tympanic cavity by a ligament.

6. THE STAPES
 The stapes possesses
1. Head
2. Neck
3. Two limbs
4. A Base
 HEAD: is small and articulates with the long process of the incus.
 NECK: is narrow and receives the insertion of the stapedius muscles.
 Two LIBMS: diverge from the neck and are attached to the oval base.
 BASE: The edge of the base is attached to the margins of the fenestra
vestibuli by a ring of fibrous tissue the anular ligament.

8. HOW THE AUDITORY OSSICLES WORK
 THE Purpose of the auditory ossicles is to transmit sound via a chain
reaction of vibrations that connects the eardrum to the inner ear and
cochlea.
 Once the vibration reach the cochlea, a hollow, snail like chamber filled
with fluid, they are translated into nerve impulses which translated into
nerve impulses which the brain interprets as sound.
 Auditory chain reaction start when sound reach eardrum, the vibrational
pressure is passed to the malleus, an articulated bone that flexes at one
of the two incudomalleolar joints
 The vibration is then passed to the incus which flexes at another
incudomalleolar joint before transferring the impulse to the stapes.

9.  The role of auditory ossciles is complete when the vibrational input is
passed to the cochlea through the oval window(opening between middle
and inner ear)
REGULATION OF SOUND:
 In addition to faciliting hearing, the auditory ossicles serve a protective
function when exposed to continuous, loud noises.
 Muscles of the eardrum called (stapedius and tensor tympani muscles)
will contract. The tightening reduces the eardrum’s ability to vibrate,
thereby limiting the movement of auditory ossicles and the impact of the
sound.
DISORDER OF AUDITORY OSSICLES:
1. Otosclerosis.
2. Chloesteatoma.
3. Genetic disorder.