The document provides an extensive overview of the anatomy and functions of the middle ear, including its cavities, components, and surgical considerations such as tympanoplasty and myringoplasty. It describes the structure and role of the ossicles, muscle actions, nerve supply, and the importance of various anatomical landmarks in relation to ear surgery. Additionally, it details the mastoid antrum and air cells relevant to ear health and disease.

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(MIDNAPORE MEDICAL COLLEGE & HOSPITAL,
WEST BENGAL, INDIA)

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3. INTRODUCTION
 Middle ear cavity is also known as tympanic cavity.
 Remember Tympanoplasty is an operative approach to
the tympanic cavity (eradicate disease from middle
ear cavity by ossicular reconstruction & improves
hearing) with or without an approach to tympanic
membrane (Myringoplasty = Type 1 Tympanoplasty).
 Middle ear together with Eustachian tube, aditus,
antrum and mastoid air cells are called middle ear
cleft.
 It is lined by secretory mucosa & filled with air.
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5. PARTS
 In relation to the tympanic membrane it is divided
into
 Epitympanum / Attic : above the pars tensa but medial to
the Shrapnell’s membrane & bony lateral attic wall
(scutum).
 Mesotympanum : lying opposite the pars tensa.
 Hypotympanum : lying below the level of pars tensa.
The portion of middle ear around the tympanic orifice of
Eustachian tube is called protympanum.
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7. BOX REPRESENTATION
 Middle ear can be compared with a six walled room
with a roof, a floor, medial, lateral, anterior &
posterior walls.
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8. ROOF
 Thin plate of bone called tegmen tympani.
 It extends posteriorly as tegmen antri to form roof
of the mastoid antrum.
 Roof separates tympanic cavity from middle cranial
fossa.
 Tegmen is bulged, called arcuate eminence due to
superior semicircular canal.
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9. FLOOR
 Separates from jugular bulb.
 Sometimes it is congenitally deficient & jugular bulb
may then project into middle ear only covered by
mucosa.
 In the floor there is carotico-jugular crest, which
can be normally distinguished by CT-scan. Anterior
to which internal carotid artery & posterior to which
jugular bulb is present.
 Inability to distinguish JB & ICA in CT-scan due to
erosion of the crest called Phelp sign.
 Seen in contrast enhanced CT-scan of glomus tumor.
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10. 10
ICA & JV
FORAMEN
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11. 11
Just focus on 11 & 12 (ICA & JB) & the crest between
them (not shown but imagine)
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12. ANTERIOR WALL
 Two openings are there
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1 : Canal for tensor tympani muscle
2 : Eustachian tube
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14. MEDIAL WALL
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 Oval window / Fenestra vestibuli – to which footplate
of the stapes attaches.
 Round window / Fenestra cochleae – covered by
secondary tympanic membrane.
 Promontory – bulged due to 1st or basal coil of cochlea.
 Processus cochleariformis – anterior to oval window a
hook like projection.
 Tensor tympani muscle after originating from canal for TT
on anterior wall hooks around this projection and attaches
to neck of malleus. Supplied by mandibular br. of trigeminal
nv (5th).
 It also marks the level of 1st genu of facial nerve, an
important landmark for surgery of facial nv.
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15. MEDIAL WALL
 Facial nerve – above the oval window a bony fallopian
canal for facial nv (horizontal / tympanic part).
 Its bony covering may sometimes be congenitally
dehiscent making the nv vulnerable to injury & infections.
 Dome of lateral semicircular canal – above the nv
canal.
 Most common site of labyrinthine fistula.
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16. 1616
3 : Oval window
4 : Round window
5 : Processus cochleariformis
6 : Dome of lateral / horizontal scc
7 : Facial nerve
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18. NARROWEST PART OF MIDDLE EAR ??
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TM
Promontory
Mesotympanum
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19. SURGICAL FLOOR OF MIDDLE EAR ??
 Width of ME = Depth of ME cavity in surgical
position.
 So shallowest part of middle ear is again
mesotympanum.
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TM
Promontory
Medial wall
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20. POSTERIOR WALL
 Lies close to mastoid air cells.
 Pyramid – bony projection
 Stapedius muscle appears from the summit of it & gets
attached to neck of stapes. Supplied by the nerve to
stapedius, a branch of the facial nerve.
 Aditus – through it attic communicates with antrum.
 Facial nerve – vertical / mastoid segment runs just
behind the pyramid.
 Gives a branch (chorda tympani) which comes out of
anterior wall (through canal of Hugier) by crossing the
middle ear simulating a hanging cord.
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21. 21
8 : Pyramid
9 : Aditus
10 : Chorda tympani nv
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22. POSTERIOR WALL
 Facial recess / Posterior sinus – depression in the
post wall lateral to the pyramid.
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Facial reccess
Laterally
Annulus
Medially
Facial nv
Inferiorly
Chorda-facial
angle
Superiorly
Fossa incudes
(short process)
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23. UNDERSTAND THE ORIENTATION
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 Facial recess is the
site for posterior
tympanotomy /
approaching middle
ear without
disturbing posterior
meatal wall.
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24. Posteriorly
Posterior wall
SINUS TYMPANI – 3D SPACE
 Medial to pyramid.
 Most common site for recurrent cholesteatoma.
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Sinus tympani
Laterally
Facial nv
Medially
Medial wall
Superiorly
Ponticulus
Inferiorly
subiculum
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lateral
Medial
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26. LATERAL WALL
 Largely by tympanic membrane.
 Lesser extent by scutum.
 Through the semitransparent tympanic membrane
this structures are visible
 Long process of incus
 Incudostapedial joint
 Round window
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27.  Erosion of scutum (arrow) is a characteristic CT
scan finding of cholesteatoma.
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28. SHORT TEST !!!
 Identify the structures :
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1. Promontory
2. Processus cochleariformis
3. Horizontal part of CN VII
4. Oval window
5. Dome of horizontal canal
6. Pyramid
7. Ponticulus
8. Sinus tympani
9. Subiculum
10. Round window
11. Tympanic plexus
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30. OSSICLES
 The ossicles conduct sound energy from the tympanic
membrane to the oval window. There are three middle
ear ossicles.
 Malleus (Hammer) : It consists of a head, neck,
handle (manubrium), a lateral and an anterior process.
It is the largest ossicle and measures 8 mm in length.
 Head and Neck: They lie in the attic.
 Manubrium (handle): It is embedded in the fibrous layer
of the tympanic membrane.
 Anterior process: bony spicule connected to
petrotympanic fissure by ligamentous fibres.
 Lateral process: It appears as a knob-like projection on
the outer surface of the tympanic membrane and provides
attachments to the anterior and posterior malleal folds.
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31.  Incus (Anvil) : It consists of following parts:
 Body and Short process: They lie in the attic. Short pr. is
connected to fossa incudis by lig. fibres in epitympanic
recess.
 Long process: It hangs vertically and medial & parallel to
malleus handle and forms incudostapedial joint with the
head of stapes by its lenticular process.
 Stapes (Stirrup) :
 This smallest bone of body measures about 3.5 mm.
 It consists of head, neck, anterior and posterior crura
and footplate.
 The footplate is positioned in the oval window by annular
ligament 31
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33. ARTICULATIONS OF THE OSSICLES
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34. LIGAMENTS
 Malleus
 Anterior ligament of Malleus: neck of malleus to ant wall of
tympanic cavity.
 Contains muscle fibers called as Laxator tympani/ Musculus externus
mallei.
 Lateral ligament of Malleus: triangular band, from post border of
tympanic inscisure to head of malleus.
 Superior ligament of Malleus: head of malleus to roof of
epitympanic recess.
 Incus
 Posterior ligament of Incus: from end of short process to fossa
incudes.
 Superior ligament of Incus: body to roof of epitympanic recess.
 Stapes
 Vestibular surf & rim of stapedial base covered with hyaline
cartilage, which is attached to margin of fenestra vestibuli by
annular ligament. 33
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35. MUSCLES
 Tensor tympani: It runs above the eustachian tube
in a bony tunnel. Its tendon turns round the
processus cochleariformis and passes laterally.
 Origin: from the bony tunnel, the cart. part of
Eustachian Tube & the adjoining part of greater
wing of Sphenoid.
 Insertion: Just below the neck of malleus.
 N/S: It develops from the 1st branchial arch and is
supplied by a branch of the nerve to medial
pterygoid, a br of mandibular division of trigeminal
nerve (CN V3).
 B/S: sup. tympanic br of middle meningeal artery
 Action : It tenses the tympanic membrane by
drawing the handle of malleus medially.
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36.  Stapedius : On contraction it dampens the loud
sounds and prevents noise trauma to the inner ear.
 Origin: Conical cavity and canal within pyramid (on
post. tymp wall).
 Insertion: It inserts to the neck stapes.
 N/S: It is developed from the 2nd branchial arch and
is supplied by a branch of CN VII (nerve to stapedius
of facial nerve)
 B/S: branches of Posterior auricular, anterior
tympanic & middle meningeal arteries
 Action: damp down excessive sound vibrations.
Opposes action of tensor tympani which pushes the
stapes more tightly into fenestra vestibuli. 36
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38. INTRATYMPANIC NERVES
 Tympanic plexus (Nerve supply of middle ear) : The tympanic
nerve plexus, which lies on the promontory, supplies to the
medial surface of the tympanic membrane, tympanic cavity,
mastoid air cells and the bony eustachian tube. It is formed
by following nerves:
 Tympanic branch of glossopharyngeal (Jacobson’s
Nerve) : It carries secretomotor fibers to the parotid
gland.
 The pathway of secretomotor fibers to the parotid gland
consists of Inferior salivary nucleus - CN IX - Jacobson’s
tympanic branch - Tympanic plexus - Lesser petrosal nerve -
Otic ganglion - Auriculotemporal nerve - Parotid gland.
 Section of Jacobson’s nerve is carried out in cases of Frey’s
syndrome.
 Sympathetic fibers : Caroticotympanic nerves come
from the sympathetic plexus, which is present round the
internal carotid artery
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39.  Chorda tympani nerve: This branch of the facial
nerve enters the middle ear through posterior
canaliculus.
 It runs on the medial surface of the tympanic
membrane.
 It lies between the malleus and long process of incus,
above the insertion of tensor tympani.
 It carries gustatory fibers from the anterior two-
third of tongue and parasympathetic secretomotor
fibers to the submaxillary and sublingual salivary
glands.
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41. FUNCTIONS OF ME
 Conduction of sound from tympanic membrane to
labyrinth.
 Impedance matching mechanism : when sound travels
from ME to IE, maximum wave is reflected back due to
impedance of labyrinthine fluid. So ME does this actions
 Lever action of ossicles : handle of malleus is 1.3 times longer
than long process of incus, providing mechanical advantage of
1.3
 Hydraulic action of tympanic membrane :
 Total area of TM – 90 sq mm.
 Effective vibratory area of TM – 55 sq mm.
 Area of footplate of stapes – 3.2 sq mm.
 Areal ratio – 17 : 1
 Total transformer ratio - 17 x 1.3 = 22 : 1
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42. 42
Total area of TM – 90 sq
mm.
Effective vibratory area
of TM – 55 sq mm.
Area of footplate of
stapes – 3.2 sq mm.
Areal ratio – 17 : 1
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43. MASTOID ANTRUM
 This air-containing space (9 mm height, 14 mm width
and 7 mm depth) is situated in the upper part of
mastoid. Vol – 1ml
BOUNDARIES -
 Roof: It is formed by the tegmen antri, which
separates mastoid antrum from the middle cranial
fossa.
 Lateral wall: It is formed by a 15mm thick plate of
squamous part of temporal bone which is marked on
the lateral surface of mastoid by suprameatal
(MacEwen’s) triangle. It is covered by postaural skin.
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44.  Medial wall: It is formed by the petrous bone and
related to the
 Posterior semicircular canal
 Endolymphatic sac
 Dura of posterior cranial fossa.
 Anterior: Anteriorly mastoid antrum communicates
with the attic through the aditus ad antrum. Medial
to lateral relations are following:
 Facial nerve canal
 Aditus ad antrum and facial recess lie between
tympanum and mastoid antrum
 Deep bony external auditory canal (EAC) 44
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45.  Posterior wall: It is formed by mastoid bone and
communicates with mastoid air cells.
 Sigmoid sinus curves downwards.
 Floor: It is formed by mastoid bone and
communicates with mastoid air cells. Other deeper
relations from medial to lateral sides are
 Jugular bulb medial to facial canal.
 Digastric ridge which gives origin of posterior belly of
digastric muscle.
 Origin of sternocleidomastoid muscle.
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46. MACEWEN’S TRIANGLE
 Linea temporalis (temporal line): A ridge of bone
extending posteriorly from the zygomatic process
(marking the lower margin of temporalis muscle and
approximating the floor of middle cranial fossa)
 EAC: Posterosuperior margin of EAC.
 Tangent: A tangent to the posterior margin of EAC .
 At birth its 2mm thick and increases at rate of 1 mm/yr
to attain full thickness of 12-15mm.
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48. 48
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49. MASTOID
 The mastoid consists of bony cortex with a
honeycomb of air cells underneath.
 Depending on development of air cells, three types
of mastoid have been described.
 Well pneumatized / Cellular – well developed air cells
with thin intervening septa.
 Diploetic – marrow spaces with few air cells.
 Sclerotic / Acellular : no cells or marrow spaces. Mastoid
antrum is small & sigmoid sinus is anteposed.
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50. 50
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51. MASTOID AIR CELLS
 The mastoid air cells are traditionally divided into several groups,
which include:
1. Zygomatic cells: In the root of zygoma.
2. Tegmen cells: Extending into the tegmen tympani.
3. Perisinus cells: Present over the sinus plate.
4. Retrofacial cells: Present round the fallopian canal of facial nerve.
5. Perilabyrinthine cells: They are located above, below and behind the
labyrinth. The cells, which are present in the arch of superior
semicircular canal, may communicate with the petrous apex.
6. Peritubal cells: They are present around the eustachian tube. These
and the hypotympanic cells communicate with the petrous apex.
7. Tip cells: These large cells lie in the tip of mastoid medial and
lateral to the digastric ridge.
8. Marginal cells: These cells, which lie behind the sinus plate, may
extend into the occipital bone.
9. Squamous cells: They lie in the squamous part of temporal bone.
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53. MUCOUS MEMBRANE OF ME
 Mucous membrane of nasopharynx is continuous with
middle ear, aditus, antrum & mastoid air cells.
 It wraps the structures of ME like peritoneum of
abdomen, dividing the cavity into various compartments.
 Better to say all the structures are outside the mucous
membrane.
 Eustachian tube :
 Cartilaginous part – pseudostratified columnar
 Bony part - columnar
 Tympanic cavity :
 Antero-inferior part – ciliated columnar
 Posterior part – cuboidal
 Epitympanum & mastoid air cells – non-ciliated, flat
epithelium.
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54. COMPARTMENTS OF ME
 Ossicles and their mucosal folds separate
mesotympanum from epitympanum (attic).
 Compartments of Epitympanum
1. Prussak’s space: Its boundaries, which limit spread
of infection to other compartments, are following:
 Lateral: Membrana flaccida (Shrapnell’s membrane)
 Medial: Neck of malleus
 Floor: Lateral process of malleus
 Roof: Fibers of lateral malleal ligament arising from neck
of malleus and inserting along the rim of notch of Rivinus
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56. 56
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57. COMPARTMENTS OF ME
2. Attic compartments:
 Transversely placed superior malleolar fold divides attic
into two compartments – smaller anterior and larger
posterior.
 The space between the lateral malleolar fold and lateral
incudal fold provides communication with Prussak’s space.
 2 compartments –
 Anterior attic compartment
 Posterior attic compartment: Superior incudal fold divides this
space into following two divisions:
 Medial space
 Lateral space
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58. 58
Postero-superior
& lateral view of
right tympanic
cavity showing
compartments &
folds of ME
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59. COMPARTMENTS OF ME
 Compartments of Mesotympanum: In the upper part
of mesotympanum there are following three
compartments.
1. Inferior incudal space: Its boundaries are following
 Superior: Lateral incudal fold
 Medial: Medial incudal fold
 Lateral: Posterior malleolar fold extending from neck of
malleus to posterosuperior margin of tympanic sulcus.
 Anterior: Interossicular fold that lies between long
process of incus and upper two-third of handle of malleus.
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60. COMPARTMENTS OF ME
2. Anterior pouch of von Troeltsch: It lies between the
following boundaries:
 Medial: Anterior malleolar fold extending from neck of
malleus to anterosuperior margin of tympanic sulcus
 Lateral: Portion of the tympanic membrane anterior to
handle of malleus
3. Posterior pouch of von Troeltsch: It is situated
between the following boundaries:
 Medial: Posterior malleolar fold extending from neck of
malleus to posterosuperior margin of tympanic sulcus.
 Lateral: Portion of the tympanic membrane posterior to
handle of malleus.
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65. KORNER’S SEPTUM
 Mastoid develops from the squamous and petrous
parts of temporal bone.
 In some cases petrosquamosal suture persists as a
bony plate called Korner’s septum, which separates
superficial squamosal cells from the deep petrosal
cells.
 During the mastoid surgery, Korner’s septum causes
difficulty in locating the antrum and the deeper
cells.
 If not recognized, Korner’s septum leads to
incomplete removal of disease during mastoidectomy.
Mastoid antrum can be entered into only after the
removal of Korner’s septum
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67. BLOOD SUPPLY
 Following branches of external and internal carotid
arteries supply blood to middle ear:
 External Carotid Artery
 Maxillary artery
 Anterior tympanic artery: Major contributor
 Middle meningeal artery
 Petrosal branch
 Superior tympanic artery: It traverses along the canal for
tensor tympanic muscle.
 Artery of pterygoid canal: Branch that runs along eustachian
tube.
 Posterior auricular artery
 Stylomastoid artery: Major contributor
 Ascending pharyngeal artery
 Tympanic branch
 Internal Carotid Artery: petrous part
• Caroticotympanic branches.
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68.  VENOUS DRAINAGE
 Veins from the middle ear cleft drain into pterygoid
venous plexus, superior petrosal sinus and sigmoid sinus.
 LYMPHATIC DRAINAGE
 The lymphatics of middle ear drain into retropharyngeal
and parotid nodes. Eustachian tube lymphatics drain into
retropharyngeal group of lymph nodes . Internal ear does
not have any lymphatics.
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69. WHICH WALL ??
69
2
1
3
4
5
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70. MEDIAL WALL
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71. PRUSSAK SPACE ??
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72. 72
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73. UNDERSTAND THE ACTUAL VIEW (LEFT EAR)
Left ear, 0° endoscope: View of the tympanic cavity after elevation of the
tympano-meatal flap. The meso-and hypotympanum as well as parts of the epi-,
retro-and protympanum are visualized.
u: umbo
m: manubrium
sp: short process
n: neck of the malleus
pr: promontory
jn: Jacobson nerve
hy: hypotympanum
fi: finiculus
sst: sinus subtympanicus
se: styloid eminence
pe: pyramidal eminence
st: stapedial tendon
isj: incudostapedial joint
fn: facial nerve
ttm: tensor tympani muscle
ttf: tensor tympani fold
ica. Internal carotid artery
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74. Development of the middle ear is not covered in this
presentation. If you are interested then please mail
me. I will try to upload it as a separate one.
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drsuraj1997@gmail.com

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