Transcript EAR

It is divided into:
External ear. 
Middle ear 
(Tympanic
cavity).
Internal ear 
(Labyrinth).

Auricle : 
Attached to the lateral 
aspect of the head.
External Auditory (Acoustic)
meatus:
A canal leading inwards. 
It is (S) shaped tube . 
(2.5 cm) in adults. 
Its lateral 1/3 is 
Cartilaginous.
It is lined with Skin. 
It contains hairs, sebaceous
and many Ceruminous
glands


Its medial 2/3 is Bony. 
Formed mainly by the 
Tympanic Plate.
It is lined by thin skin. 
Nerve Supply : 
Auriculotemporal nerve.
Auricular branch of the 
vagus.
The meatus has to be
straight.
It is pulled
In Children:
Straight backward or
downward and
backward.
In Adults : 
Upward and 
backward.

It is an oval, thin 
semitransparent
membrane (1 cm)
in diameter.
It forms a Partition
between the
external meatus
and the tympanic
cavity.

A shallow cone like 
central depression , its
peak is the Umbo.
Cone of light radiates 
antero inferior from the
umbo.
Pars Flaccida:

The thin superior part of
the membrane.
Pars Tensa: 
The rest of the 
membrane.
It is thick and taut. 

The tympanic membrane
is extremely sensitive to
pain.
Outer surface (mainly): 
Auriculotemporal nerve 
Auricular branch of the 
vagus.
Internal surface: 
Glossopharyngeal nerve.

It is an air- filled 
mucous membrane
lined space in the
temporal bone.
It is between: 
Laterally: 
The Tympanic 
membrane.
Medially: 
The lateral wall of the
inner ear.

(1) Tympanic Cavity:
A space directly 
internal to the
tympanic membrane.
(2) Epitympanic 
Recess:
A space superior to 
the tympanic cavity.

(1) Anterior: 
Nasopharynx 
(2) Postero 
superior:
Mastoid air cells.

Tegmental Wall: 
A thin plate of bone 
(Tegmen Tympani) on
the anterior surface of
the petrous part of
temporal bone.
It separates the cavity
from:
Middle Cranial Fossa.
Jugular wall: 
It is a thin plate of 
bone.
It separates the cavity 
from the Superior Bulb
of IJV.
It may be deficient or 
replaced by fibrous
tissue.
Membranous: 
Almost totally it is the
Tympanic Membrane.
Superiorly: 
Epitympanic Recess. 

Labyrinthine 
1. Promontory: 
A central bulge . 
Produced by the basal coil of the
Cochlea
2. Tympanic Plexus. 
On the mucous membrane of the
promontory.
3. Fenestra Vestibuli: 
(Oval Window) 
It is above and behind the 
Promontry.
4. Fenestra Cochlea (Round 
window).
The windows lead to Perilymph of
internal ear.




5. Prominence of 
facial canal:
posterior and 
superior to the oval
window.
Produced by the 
Facial nerve in its
canal.
6. Prominence of 
lateral semicircular
canal.
A pathological 
process affecting the
mucosa of the Oval
window and the
mastoid process.
They are 
transformed into
bone.
It is complicated by 
Deafness.
Carotid : 
Lower : 
A thin plate of bone. 
It separates the tympanic
cavity from the Carotid
Canal.
Upper: Two openings 
Upper smaller: for the 
Tensor Tympani.
Lower larger: for the 
Auditory Tube.

Mastoid area : 
A. Aditus 
A large irregular opening 
posterior to the epitympanic
recess.
B. Mastoid antrum : 
A cavity continuous with air filled
spaces within the mastoid
process.
C. Pyramid: 
The tendon of Stapedius muscle 
emerges from its apex.

Roof : Tegmen Tympani. 
Floor : Many openings 
To communicate with the mastoid
air cells.
Anterior : 
Middle ear & Aditus. 
Posterior: 
Sigmoid Sinus & Cerebellum. 
Lateral: 
Floor of Suprameatal Triangle. 
Medial: 
Posterior Semicircular Canal.


1. Auditory
Ossicles.
2. Muscles.
3. Nerves. 


They extend from the tympanic 
membrane to the oval window.
They are present at Birth. 
Not covered by Periosteum. 
Malleus: 
The largest and attached to the 
tympanic membrane.
Stapes: 
Occupies the oval window . 
Incus: 
Between the two bones. 
Their decreased mobility in old 
age is responsible for degrees of
Deafness.
It lies in a bony canal 
above the
Pharyngotympanic tube.
Insertion: 
Handle of the malleus. 
Action: 
Pulles the handle 
medially.
Tenses the tympanic 
membrane.
Reduces the amplitude of
its oscillations.

The smallest voluntary muscle of
the body.
Origin: 
From inside the pyramidal 
eminence.
Insertion: 
Neck of the stapes. 
Action: 
Pulls the stapes posteriorly. 
Reduces the oscillatory range and
prevents its excessive
movements.
Nerve supply : Facial nerve. 


A branch of 
Glossopharyngeal nerve.
Passes through the floor of 
the middle ear and onto the
Promontry.
Gives: 
Tympanic Plexus: 
It associates the 
Caroticotympanic Plexus to
supply mucous membrane of
middle ear.
Lesser Petrosal nerve : 
To Otic Ganglion. 
Enters: 
1.Internal acoustic 
meatus in close company
with the 8th nerve.
2. Facial Canal. 
It continues laterally 
between the inner and
middle ears.
It expands to form the 
Geniculate Ganglion.
At the posterior wall:
Curves downward in
a vertical direction.
Lies : 
Medial to the Aditus.
Behind the Pyramid.
Exits: 
Through the 
Stylomastoid
Foramen.




1. Greater Petrosal 
nerve.
It is the first branch 
from the Geniculate
Ganglion. 
It carries preganglionic
parasympathetic to the
Pterygopalatine
Ganglion.
It supplies: 
Lacrimal , Nasal and 
Palatine glands.

2. Nerve to 
Stapedius.
3. Chorda Tympani:
It arises just before
the facial nerve
exits.
It ascends to enter
the middle ear
through its
posterior wall.



Connects the Tympanic 
Cavity to the
Nasopharynx.
Its Postero lateral 1/3 is 
bony.
The remainder is 
Cartilaginous.
Its walls are normally in 
apposition.
The tube is actively 
opened by swallowing
and yawing
Function : 
Equalizes pressure in the
middle ear with the
atmospheric pressure.
It is a pathway of 
infection from the throat
to the tympanic cavity
and mastoid air cells.
Nerve supply : tympanic
plexus.


A series of bony 
cavities in the
Petrous part of
temporal bone.
It is composed of: 
Cochlea. 
Vestibule. 
Semicircular Canals.
They contain 
Perilymph.

Cochlea: 
It is shell shaped . 
Its first turn produces the 
Promontory.
Vestibule : 
It is in a central position. 
It has the Oval and Round 
Windows in its lateral wall.
Semicircular canals : 
Posterior, superior and Lateral.
They communicate with the 
Vestibule.

It consists of: 
Four Ducts: 
Cochlear 
Three Semicircular 
Two Sacs: 
Utricle. 
Sacuule. 
It is filled with 
Endolymph.
It is separated from the
periosteum of the bony
labyrinth by Perilymph.

The cochlea is divided into 
two canals containing
Perilymph by the centrally
located cochlear duct.
The duct has : 
Roof : Vestibular 
membrane.
Floor : Basilar membrane. 
The Spiral Organ (organ of 
hearing) rests on the
basilar membrane.
Utricle. 
Sacule 
Three Semicircular 
Ducts.
The Utricosaccular Duct
establishes
continuity between all 
components of the
membranous labyrinth.

The Endolymphatic 
Duct branches from it.
It emerges onto the 
posterior surface of
the petrous part of
the temporal bone.
It expands to form an 
Extradural Pouch
Endolymphatic Sac.
Divides into : 
A. Vestibular nerve : 
It enlarges to form the 
Vestibular Ganglion.
It supplies: 
Three semicircular ducts. 
Utricle & Saccule. 
B. Cochlear nerve: 
It enters the base of the 
cochlea.
It innervates the receptors in
the Spiral Organ.
