2. DR. RAJU MANDAL
JUNIOR RESIDENT
DEPARTMENT OF ENT
MEDICAL COLLEGE, KOLKATA

3. WHAT IS MIDDLE EAR?
 Conventionally, the
ear has been divided
into three parts:
1. External Ear
2. Middle Ear
3. Internal Ear

4. THE MIDDLE EAR CLEFT
 The middle ear cleft consists
of:
1. Tympanic cavity
2. Eustachian tube
3. Mastoid air cell system

5. THE TYMPANIC CAVITY
 It can be divided into three parts-
• Epitympanum- Lies above level of the
malleolar fold.
It contains- head of the malleolus, body
of the incus,ossicular ligaments &
mucosal fold.
• Mesotympanum-Lies opposite the
pars tensa of tympanic cavity.
It contains- long process of incus
stapes, mucosal folds
• Hypotympanum-Lies below the level
of inferior part of tympanic sulcus.
It contains-glomus body and bulge of
jugular bulb.

6. THE TYMPANIC CAVITY
 It is like a six sided box –
1. Roof (Tegmental wall)
2. Floor (jugular wall)
3. Lateral wall(Membranous wall)
4. Medial wall (Labyrinthine wall)
5. Posterior wall (Mastoid wall )
6. Anterior wall(Carotid wall)

7. R00F OF TYMPANIC CAVITY
 Formed by tegmen tympani ( both petrous and
squamous ) which separates the middle ear
space from the middle cranial fossa
 Veins to superior petrosl sinus passes through
petrosquamous suture
 This suture line not closed till adult life, so is a
route of infection into extradural space in
children.

8. FLOOR OF TYMPANIC CAVITY
 It is formed by pneumatised
bone, or may be deficient
when covered by muscle or
mucous membrane
 It separates from jugular bulb
 At the junction of floor and
medial wall of the cavity a small
opening present
 Its passes tympanic branch of
glossopharyngeal nerve

9. LATERAl
WALL OF TYMPANIC CAVITY
 It is formed by-
 Superiorly-bony lateral wall of
epitympanum
 Centrally-tympanic mmbrane
 Inferiorly-bony lateral wall of
hypotympanum

10. LATERAL WALL OF TYMPANIC CAVITY
 Lateral epitympanic wall-
 Wedged shaped
 Sharped inferior portion called
scutum, which is very thin &
easily eroded by choleteotoma.
 Petrotympnic fissure-
Open anteriorly just above
attachment of tympanic
membrane. Its-
 receives anterior malleolar
ligament
 Transmit anterior tympanic branch
of maxillay artery

11. LATERAL WALL OF TYMPANIC CAVITY
 Chorda tympani nerve-
 Enters through anterior canaliculus
 Runs posteriorly between the
fibrous and mucosal layers of
tympanic membrane
 Enters posterior canaliculus
 Runs obliquely downwards and
medially through the posterior
wall to reach facial nerve
 Point of entry to facial nerve is
variable, usually inferior 13 rd
of facial canal in ant surface

12. ANTERRIOR WALL OF TYMPANIC CAVITY
 Lower third-
 Consists of thin bone covering
internal carotid artery
 It is perforated by sup.& inf.
corticotympanic nerve carrying
sympathetic fibres to tympanic
plexux from internal carotid
artery

13. ANTERIOR WALL OF TYMPANIC CAVITY
 Middle third-
Comprise tympanic opening of the
Eustachian tube(5mm*2mm)
 Upper third-canal
containing the tensor tympani
muscle
Small niche anterior to ossicular
head called anterior epitympanic
sinus-which can hide residual
cholesteotoma

14. MEDIAL WALL OF TYMPANIC CAVITY
 Central portion occupied by a
rounded elevation- called
promontory.
 A small Groove over it contains
tympanic plexus

15. MEDIAL WALL OF TYMPANIC CAVITY
 Behind & above the
promontory, lies oval
window.
 Oval window connects
tympanic cavity with
vestibule.But it is closed by
foot plate of stapes
 It is kidney shaped(3.25 mm
long & 1.75 mm wide)

16. MEDIAL WALL OF TYMPANIC CAVITY
 The round window is
triangular in shape
 It has Ant., Post-Sup, &
Post-Inf wall
 about 2.3*1.9 mm size
 Separated from scala
tympani by secondary
tympanic membrane

17. MEDIAL WALL OF TYMPANIC CAVITY
 Posterior extension of
promontory-Subiculum
 Post-Sup & Post-Inf walls
of round window meets
posteriorly & forms-Sinus
Tympani
 It is most inaccessible part of
middle ear & mastoid

18. MEDIAL WALL OF TYMPANIC CAVITY
 Fallopian canal or facial canal
runs above promontory and oval
window in an antero-posterior
direction.
 Anterior most part of the canal is
processus cochleariformis which
attached to tendon of tensor
tympani muscle
 Behind the oval window, the
facial canal starts to turn
inferiorly as it begins to descent
in the posterior wall

19.  Smooth lateral surface of facial canal may
have microdehicense, which diagnosed by
visibility of some straight blood vessel over
canal

20.  Above processus cocleaformis
a small swelling corresponds to
genuculate ganglion
 More posteriorly facial nerve
related to lateral semicircular
canal
 During cortical
mastoidectomythe triangular
realationship between lat
semicircular canal,short process
of incuss &facial nerve is very
helpful

21. POSTERIOR WALL OF TYMPANIC CAVITY
 Upper part has a irregular
opening-aditus of antrum
 Below the aditus is the
Fossa incuidis-which
houses short process of
incus and its suspensory
ligament
 Below fossa incuidis ,a
conical projection called
Pyramid-attached to
stapedius muscle & tendon

22. POSTERIOR WALL OF TYMPANIC CAVITY
Facial recess- bounded
medially by the facial
nerve and laterally by the
tympanic annulus
It allows posterior
tympanotomy

23. POSTERIOR WALL OF TYMPANIC CAVITY
 Posterior extension of
mesotympanumdeep to
facial nerve and
promontory –called Sinus
Tympani
 Cholesteotoma from this
space is extremely difficult
to eradicate

24. CONTENTS OF THE TYMPANIC CAVITY
 The ear ossicles & their ligaments- Malleus,
Incus and Stapes
 The muscles- Stapedius and Tensor Tympani
 Nerves-ChordaTympani and Tympanic plexus

25. OSSICLES OF TYMPANIC CAVITY

26. CONTENTS OF THE TYMPANIC
CAVITY
 MALLEUS >
 Largest ossicles- length about
9 mm
 Three parts- head, neck &
handle or manubrium
 Head lies in the
epitympanum.Head has a facet
on postero medial surface for
articulation with body of the
incus
 Handle runs downwards,
medially and slightly backwards
between the mucous and
fibrous layers of TM

27. CONTENTS OF THE TYMPANIC
CAVITY
 From the anterior process, a
slender anterior ligament
arises to insert into the
petrotympanic fissure
 Lateral process receives the
anterior and posterior
malleolar fold
 The tendon of the tensor
tympani is inserted into a
small projection on the
medial surface of the
handle

28. CONTENTS OF THE TYMPANIC
CAVITY
 INCUS>
• It has three parts-
Body,Short process &
Long process
• Body has a facet to
articulate with
malleus.Body is
suspended by superior
incuidal ligament that is
attached to tegmen
tympani.

29. CONTENTS OF THE TYMPANIC
CAVITY
 INCUS>
• Short process projects backwards
in the fossa incudis to which it is
attached by short suspensory
ligament
• Long process projects in
mesotympanum medial to HOM.
• At tip of Long process , lenticular
process present( fourth ossciles)
which articulate with head of
stapes.

30. CONTENTS OF THE TYMPANIC
CAVITY
 STAPES>
• Two crura arise from the neck
and join the footplate
• The footplate is about 3 mm
long and 1.4 mm wide; it lies in
the oval window where it
attached to the bony margin by
the annular ligament
• Head articulates with the
lenticular process of incus
• Stapedius tendon inserts into
the neck and posterior crus

31. Ligaments of middle ear

32. CONTENTS OF THE TYMPANIC
CAVITY
MUSCLES>
 The stapedius muscles-
Arises from the walls of
the conical cavity within
the pyramid and insert
into the stapes.
 Supplied by a branch of
the facial nerve .

33.  The tensor Tympani-
Arises from the walls of the
bony canal lying above the
ET, cartilegenous portion of
the ET & the greater wings
of the sphenoid
 Turns at processus
cochleaformis
 Inserts at handle of the
malleus
 Supplied by branch of
mandibular nerve

34.  MUCOSA>
HISTOLOGICALLY-
1. ET- lined by cilliated columner epithelium.In
cartilajenous part pseudostratified
columnar and in bony part several mucous
gland in submucosa present
2. Tympanic cavity-cilliated columner in anterir
& inferior part and cuboidal in posterior part
3. Epitympanumand mastoid air cells- by flat
non cilliated epithelium

35.  Three distinct mucocillary pathway present-
Epitympanic, Promonterial, and
Hypotympanic, the latter is the largest
 Each coalesces at the tympanic orrifice of ET

36.  MUCOSAL FOLDS>
• Like peritoneum in abdomen it covers
ossicles,their ligaments,muscles, tendons in
middle ear cavity
• It carry blood supply to &from contents of
middle ear
 These folds separates middle ear in
compartments-As a result only route for
ventilation from epitympanic space to
mesotympanum is small opening between
various mucous fold-Anterior & Posterior
isthmus tympani.

37.  MUCOUS FOLD>
Described by
PROCTOR

38. BLLOD SUPPLY OF THE TYMPANIC
CAVITY
 Middle ear is supplied by the following
 1)Two main arteries
a)Anterior tympanic branch of maxillary artery
b)Stylomastoid branch of posterior auricular artery
 2)some minor arteries
 a)Petrosal branch of middle meningeal artery
 b)Superior tympanic branch of middle
meningeal artery
 c)Branch of artery of pterygoid canal
 d)Tympanic branch of internal carotid
 d) Inferior tympanic branch of ascending
pharyngeal artery.

39. Blood supply

40. NERVE SUPPLY OF MIDDLE EAR
 It is by tympanic plexus which is formed by the-
 tympanic branch of the glossopharyngeal nerve (Jacobson's
nerve) and
 caroticotympanic nerves, which arise from the sympathetic
plexus around the internal carotid artery.
 The nerves form a plexus on the promontory and provide
the branches to the mucous membrane lining the tympanic
cavity, Eustachian tube and mastoid antrumand air cells.
 The plexus also provides branches to join the greater
superficial petrosal nerve and the lesser superficial petrosal
nerve that contains all the parasympathetic fibres of the
glossopharyngeal nerve

41. `
 MUCOUS FOLD>
PRUSSAKS SPACE-Bounded
by-
1. Laterally-Pars flaccida
2. Medially-neck of the malleus
3. Above-anterior malleolar ligament
4. Below-short process of the malleus
This place can play an important role in the
retention of the keratin and subsequent
devolopment of cholesteotoma.

42. EUSTACHIAN TUBE
 Links middle ear with nasopharynx.
 Length 36 mm.
 Lateral bony segment – 12 mm.
 Medial cartilagenous segment – 24 mm.
 Narrowest portion is the Isthmus.
 Caroid artery and the Tensor tympani
muscle are separated from the tube by
thin plates of bones.
 Opens in the nasopharynx behind and
below the posterior end of inferior
turbinate.
 Behind the torus is the fossa of
Rosenmuller

43. The Mastoid Air Cell
System
 Mastoid can be
 Well pneumatised
 Diploetic
 Sclerotic
 Honeycomb of air cells
 Divided into many
groups as per their
anatomical location

45. Thank
You