15. Chorda tympani..enters medial surface of
fissure through separate canaliculus (canal of
Huguier) runs posterior then to fibrous and
mucosal layers, across upper part of handle
of malleus, along the membrane but below
the level of posterior malleolar fold
Then enters the posterior canaliculus
obliquely and medially downward,through the
posterior wall of tympanic cavity to reach
facial nerve
16. During cortical mastoidectomy the fibrous
strands of tympanomastoid suture can often
be confused with corda tympani although the
angle of white strands of suture lines
different from angle of corda
17.
18. Tegmen tympani..both petrous andsquamous
portion of temporal bone form it
Petrosquamous suture,as it does not close till
adult life,can lead to infection in extradural
space in children
Veins..superior petrosal sinus
19.
20. Compact or pneumatised bone
Separates the hypotympanum from the dome
of jugular bulb
Thickness varies
floor may be deficient..here jugular bulb is
covered by fibrous tissue and mucous
membrane
At the Junction of floor and medial wall
tympanic branch of 9th nerve opens into
middle ear from origin below the base of
skull.
21. Lower one third
thin plate of bone covering carotid artery
perforated by sup and inf caroticotympanic
nerves
Middle one third
orifice of Eustachian tube
above this opening is canal for tensor
tympani muscle
22. Upper one third
anterior epitympanic recess
small niche anterior to ossicular head
can hide residual Cholesteatoma in canal
wall up surgery
27. Covers part of the basal part of cochlea
Contains nerves forming tympanic plexus
Tympanic branch of ninth nerve may be
covered by bone forming a small canal
28.
29. Behind and above the oval window
Kidney shaped
Connects tympanic cavity with the vestibule
closed by stapes footplate and annular
ligament
Size 3.25×1.75
30. Lies below and behind the oval window
Separated by subiculum(post extension of
promontory)
Ponticulus..another ridge above subiculum
and runs to pyramid on the posterior wall
Sinus tympani is where ponticulus and
subiculum meet
RWM is 2.3×1.9.
It is placed at right angles to plane of stapes
foot plate
31.
32. Facial nerve canal,also called fallopain canal
Runs above promontory and oval window in
anterosuperior direction
Smooth rounded lateral surface has
microdehiscenses
Along the line of nerve two or three blood
vessels are visible(straight)
This canal is marked anteriorly by processus
cochleariformis and behind by the oval
window
33. Processus cochleariformis is a curved piece of
bone housing tensor tympani muscle tendon
Behind the oval window facial canal starts
inferiorly
….
34.
35.
36. Aditus and antrum
Fossa incudus
Pyramid
Canal within the pyramid curves downwards
and backwards to join descending portion of
facial nerve canal
37.
38. Groove between pyramid facial nerve and
annulus of tympanic membrane
Shallow lower down
Medially is facial nerve
Laterally tympanic annulus
Corda tympani running obliquely through
wall between the two
Posterior tympanotomy
39. Posterior extent of mesotympanum
Lies deep to promontory and facial nerve
Most inaccessible site
Cholesteatoma in posterior wall is difficult to
eradicate
Worst region to access is above the pyramid
posterior to intact stapes and medial to facial
nerve
Retrofacial appraoch not possible because
posterior SCC blocks access
56. Malleus
Largest
9mm in length
Head in epitympanum
Suspended by superior malleal ligament
Saddle shaped facet on posteromedial surface
Articulates with the incus..a synovial joint
57. Below neck is the lateral and anterior process
of malleus
Lateral process receives ant and post folds
from tympanic annulus
Handle
downwards medially and backwards
Between mucosal and fibrous layer
Closely attached to membrane at lower end
fine web of mucosa
ossicular reconstruction
58. Body
Two processes
Short process
Long process
Lenticular process
60. Head
Points laterally
Stapedius tendon gets inserted over the post
part of neck and upper portion of post crus
Crura arises from broader lower part of neck
and ant crus is thinner and less curved than
the post one
61. Foot plate
Convex superior margin
Almost straight inferior margin
Curved ant and post ends
Long axis is horizontal and post end slightly
lower than the anterior
3cm long
1.4mm wide
Sesamoid bone ..fourth ossicle
62.
63.
64.
65. Stapedius
Origin..wall of conical cavity within the
pyramid and from downward curved
continuation of this canal in front of
descending portion of facial canal
Supplied by small branch of facial nerve
66.
67.
68. Origin is wall of bony canal above eustachain
tube,cartilaginous portion of tube, greater
wing of sphenoid
Passes backward into tympanic cavity,along
medial wall little below facial nerve
Enters processus cochlearformis held by
transverse tendon latertally
Medial aspect of malleus head
Supplied by mandibular nerve via branch
from medial pterygoid nerve
69. Tensor tympani
Inserts on the malleus and acts to tense the
tympanic membrane reducing the
effectiveness of sound transmission, protecting
the inner ear during loud sounds.
Innervation from a branch of the mandibular
nerve (V3 of CN V).
70.
71.
72. Tympanic branch of 9th nerve,also called
jacobson’s nerve
Caroticotympanic nerves
Supplies mucosal layer of TM……
73.
74.
75. Mucus secreting
Respiratory type
Cilia bearing
Three distint mucociliary pathways
Epitympanic
Promontarial
Hypotympanic(largest)
These pathways coalesce at tympanic orifice
of eustachain tube
76. Mucosa covers ossicles and tendons
Ventilation of epitympanic space…
Ant and post istmic tympani
Prussack’s space
77. Length
45 degrees forwards and medially
Bony and cartilaginous parts
Mucosa
78. Length
Isthmus
Relation with tensor tympani
Relation with carotid canal
Cross section
79. Length
Medial and lateral cartilage
Fixed to base of skull between petrous part
and greater wing of sphenoid
Ends at root of medial pterygoid plate
Back
Front
Apex
80. S.No BRANCH PARENT ARTERY REGION SUPPLIED
1 ANT
TYMPANIC
MAXILLARY TM,MALLEUS,INCUS,ANT
TYMPANIC CAVITY
2 STYLOMASTOI
D
POST AURICULAR POST PART OF TYMPANIC
CAVITY,STAPEDIUS MUSCLE
3 MASTOID STYLOMASTOID MASTOID AIR CELLS
4 PETROSAL MIDDLE
MENINGEAL
ROOF OF MASTOID AND
ROOF OF EPITYMPANUM
5 SUP
TYMPANIC
MIDDLE
MENINGEAL
MALLEUS ,INCUS, TENSOR
TYMPANI
6 INF TYMPANIC ASCENDING
PHARYNGEAL
MESOTYMPANUM
7 BRANCH ARTERY OF
PTERYGOID CANAL
MESO AND HYPOTYMPANUM
8 TYMPANIC
ARCHES
INTERNAL CAROTID MESO AND HYPOTYMPANUM
81. Anatomic Considerations
• Epitympanum
– Above short process
of malleus
– Contains head of
malleus, body of
incus and associated
ligaments and
mucosal folds
– Pars flaccida lacks
support from a
fibrous middle layer
