The middle ear cavity is located between the tympanic membrane and inner ear. It contains the auditory ossicles (malleus, incus, stapes), muscles (tensor tympani, stapedius), and is connected to the nasopharynx via the Eustachian tube. The cavity has thin bony walls that separate it from important structures like the cranial fossa and carotid artery. The ossicles transmit sound vibrations from the tympanic membrane to the inner ear.

1. Presenter -Dr.Razal M Sherif
Moderator -Dr.Jyothi Swarup R

2. THE MIDDLE EAR CLEFT
• Eustachian Tube
anteriorly
• Middle ear
Cavity/Tympanic Cavity
• Aditus
• Mastoid Antrum
• Mastoid Air Cells
posteriorly

3. Middle Ear Cavity
• The tympanic cavity
o irregular, air-filled space within the temporal bone
o between the tympanic membrane laterally and the
osseous labyrinth of inner ear medially.
• Six sided Cavity
o Roof
o Floor
o Anterior Wall
o Posterior Wall
o Medial Wall
o Lateral Wall
• Contains auditory ossicles ,Intratympanic Muscles

5. ROOF
 Is a thin bony plate
 separates the middle ear from the middle cranial fossa
 called as Tegmen tympani
 formed by both the petrous and squamous portions of the
temporal bone .
 Petrosquamous suture line,
 does not close until adult life,
 can provide a route of access for infection into the middle
cranial fossa from middle ear in children.

6. FLOOR
• Thin bone separates the cavity from the dome of
the Jugular bulb.
• In some cases the floor may be deficient and the
jugular bulb is then covered only by fibrous tissue
and a mucous membrane.

7. LATERAL WALL
• Main part is formed By the Tympanic membrane.
• Superiorly an area of Bone called SCUTUM (outer
attic wall.)

8. ANTERIOR WALL
• The lower-third of the anterior wall
o consists of a thin plate of bone covering the internal
carotid artery
• The middle-third comprises
o the tympanic orifice of the Eustachian tube, which is oval
and 5 x 2mm in size.

9. MEDIAL WALL
separates the Middle ear from the Inner ear.
• Promontory-
o bulging part of on the medial wall which overlies the basal
turn of the cochlea
o has small grooves on its surface containing the nerves
which form the tympanic plexus.
• Tympanic plexus

10. • Oval Window
o Behind and above the promontory is the oval window
o that connects the tympanic cavity with the vestibule,
closed by the footplate of the stapes
o it is 3.25 mm long and 1.75 mm wide.
• Round window
o RW membrane is usually out of sight, obscured by the
overhanging edge of the promontory

11. Ponticulus & Subiculum
• Two small bony projections
are present on the medial
wall, posterior to promontory.
• Ponticulus
o Is the upper projection
posterosuperior to
promontory.
o Above the ponticulus is the
Oval Window
• Subiculum
o Lower projection
posteroinferior to promontory
o Below the subiculum is the
round window

12. • Facial Nerve canal (or Fallopian canal)
o runs above the promontory and oval window in an
anteroposterior direction.
• Processus cochelariformis
o a curved projection of bone on which the tendon of the
tensor tympani muscle takes a hook and turns laterally to
get attached to neck of malleus.
o This forms the landmark for 1st genu of facial nerve –
Posterosuperior to processus cochelariformis

13. POSTERIOR WALL
• The posterior wall is wider above than below.
• Aditus - A large irregular opening in its upper part
• Fossa incudis – A small depression below the aditus,
it houses the short process of the incus and its
suspensory ligament.
• Pyramid - a small hollow conical projection with its
apex pointing anteriorly.
o This houses the stapedius muscle and tendon, which inserts
into the posterior aspect of the neck of stapes.
o Nerve to stapedius runs through the hollow canal with in
the pyramid.

14. Facial Recess & Sinus
tymapni
Facial recess - A 3D space situated between the
• tympanic annulus and chorda tymapni laterally
• Pyramid and vertical portion of facial nerve
medially
Sinus tympani – A 3D space situated between
• Pyramid and vertical portion of facial nerve laterally
• Ponticulus medially
• Also extends deep to promontory
• the most inaccessible site in the middle ear
• Cholesteatoma which has extended to the sinus tympani is
extremely difficult to eradicate

16. Division Of Middle Ear Cavity
• EPITYMPANUM/ATTI
C
• MESOTYPANUM
• HYPOTYMPANUM

17. EPITYMPANUM/ATTIC
• Middle ear cavity above the level of anterior and
posterior Malleolar folds
• Contains
o Head of Malleus, Body of incus, ossicular ligaments and
Mucosal folds.
Prussack Space
• Space between Pars flacida laterally and Neck of
Malleus medially.
• It is the primary site of acquired Cholesteatoma

18. MESOTYPANUM
• Part lying Medial to pars Tensa
o and its air filled space
o Conatins
• handle of MALEUS
• long process of Incus,
• Stapes

19. HYPOTYMPANUM
• Part lying below the lower margin of Tympanic
membrane
• Contains
o Bulge produced by the jugular Bulb
• If the floor is deficient thus jugular bulb may project
into tympanic cavity.

20. Contents Of Middle Ear
• Ossicles
o Malleus
o Incus
o Stapes
• Muscles of Tympanic Cavity
o Tensor Tympani
o Stapedius Muscle

21. The Malleus
• Largest of the three ossicles - 9mm length
• It Has Head, Neck, Anterior and Lateral Process,
Handle
o Suspended by the superior ligament between head and
the tegmen tympani.
• Head has saddle - shaped facet on its
posteromedial surface
o to articulate with the body of the incus.
• An anterior ligament arises from the anterior process
to insert into the petrotympanic fissure.

22. Head
Neck
Anterior
Process
Handle
Lateral
Process

23. The Incus
• It has a Body, Short Process and a long process and
a lenticular process
• body of the incus
o is suspended by the superior incudal ligament that is
attached to the tegmen tympani.
• Long process
o extends downwards behind the handle of malleus
o articulates with the head of the stapes by its lenticular
process.

24. • Short process
o Lodges in the fossa incudis
• Lenticular process
o Sometimes been called the fourth ossicle because of its
incomplete fusion with the tip of the long process

25. Body
Short
Process
Facet
Lenticular
Process
Long
Process

26. The Stapes
• Shaped like a stirrup
• Consists of a head, neck, the anterior and posterior
crura and a footplate.
• The Head points laterally and has a small cartilage-
covered depression for a synovial articulation with
the lenticular process of the incus
• The foot plate directs medially and closes the Oval
window.
• Stapedius tendon inserts into the posterior part of
the neck and upper portion of the posterior crus.

27. Anterior Crus
Foot Plate
Head
Neck
Posterior Crus

28. Tympanic Plexus
• It lies over the promontory
o Tympanic Branch of Glossopharygeal Nerve (Jacobsons
Nerve)
o Sympathetic fibers from plexus round internal carotid
artery.
• It supplies
o Tympanic membrane(mucosal Surface)
o Tympanic Cavity
o Mastoid air cells
o Bony estuation tube.
o Carries secrtomotor fibers for parotid gland.

30. Chorda Tympani Nerve
• Branch of Facial Nerve
• Arises from the vertical segment of facial nerve below
the pyramid
• Crosses the posterior tympanic annulus
• Runs over the posteror malleloar fold and in between
the handle of the malleus and long process ,above the
attachment of the tensor tympani
• Leaves the middle ear through the canal of HUGAIER in
the anterior wall
• It carries the taste sensation from ant 2/3 of tongue and
secretomotor fibers to sub maxillary and sub lingual
salivary glands.

31. Muscles In the Tympanic
Cavity
• Tensor Tympani
o Origin –
• cartilaginous part of Eustachian tube
• Bony canal over ET
• greater wing of sphenoid.
o Lies above the Eustachian tube
• enters the middle ear via the canal for tensor tympani in the anterior
wall above the Eustachian tube opening.
o Hooks around the processes cochelariformis on the posterior wall and
then changes the direction laterally and get inserted into neck of malleus.
o Action
• It tenses the tympanic membrane, by pulling the malleus medially
and protects from barotrauma.

33. • Stapedius Muscle
o Orgin - From the Pyramid in the posterior
wall
o Insertion - Neck Of Stapes
o Supplied by Facial Nerve (Nerve to
Stapideus)
o Action - Pulls the Stapes Laterally
(Prevents Barotrauma)

35. Mastoid Process And Air Cells
• Mastoid Process
o Part of temporal bone and situated behind the ear.
o Development by 1 year.
o Based on the degree of pneumatisations
• Celluar – 80% - Fully pneumatised
• Sclerotic – Cells are replaced by dense bones.
• Diploeic – Cells are less and small.

36. o Mastoid antrum
• Biggest and most consistent air cell
• Connected anteriorly to tympanic cavity via the aditus
and posteriorly to other air cells.
• Relations
o Roof – Tegment antri – seperates from middle
cranial fossa.
o Floor – Mastoid portion of temporal bone
o Medial wall – Petrous portion of temporal bone
o Lateral wall –Squamous portion of temporal bone

38. • Mac Ewans triangle
o Landmark for mastoid antrum
o Suprameatal crest above
o Tangential to posterior meatal wall cutting the supra
meatal crest
o Posterior margin of EAC
• Antrum lies postero superior spine of henle.

39. EUSTACHIAN TUBE
• Connects middle ear cavity to nasopharynx.
• From the anterior wall of middle ear it passes
downwards, forwards and medially.
• Length 36mm
o Lateral 1/3rd Bony
o Medial 2/3rd is cartilaginous.
• The pharyngeal end situates 1cm behind and a little
below the end of inferior turbinate.

40. • Functions of ET
o In resting stage collapsed.
On chewing and yawning it opens up.
Helps to equalize air pressure between middle ear and
nasopharynx.
o Controls ventilation of middle ear cleft.
o Helps drainage from middle ear.
• Muscles attached to ET
o Tensor tympani
o Tensor palati
o Levator palati
o Salpingopharynx.