The tympanic cavity has six walls that form a box-like structure: the roof, floor, lateral wall, medial wall, posterior wall, and anterior wall. Key structures include the promontory on the medial wall, which contains the oval and round windows. The chorda tympani nerve passes through the lateral wall. The Eustachian tube opening is located on the anterior wall. Important anatomical relationships include the facial nerve canal along the medial wall and posterior wall.

2. 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)

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

4. 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 a small opening
present
 Its passes tympanic branch of
glossopharyngeal nerve

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

6. 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

7. 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

8. 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

9. 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
recess-which can hide residual
cholesteotoma

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

11. 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)

12. 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

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

14. MEDIAL WALL OF TYMPANIC CAVITY
 Fllopian canal or facial canal
runs above pomontory 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
facianl canal starts to tur
inferiorly as it begins to descent
in the post wall

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

16.  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

17. 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 incuss and its
suspensory ligament
 Below fossa incuidis ,a conical
projection called Pyramid-attached
to stapedius muscle
& tendon

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