ANATOMY OF middle EAR

2.  Overview
 Middle ear cleft
 Walls of middle ear
 Contents of middle ear
 Blood supply of middle ear

3.  The middle ear cleft includes
 the tympanum (middle ear cavity proper),
 the Eustachian tube, and
 the mastoid air cell system.

4.  The tympanic cavity is an air filled irregular
space contained within the temporal bone.
 three auditory ossicles
(malleus, incus and stapes) with their
attached muscles,
chorda typani nerve,tympanic plexus,
blood vessels
 Whole cleft lined by respiratory epithelium
{ciliated columnar epithelium } ,
 in the eustachian tube and antero inferior
part of tympanic cavity
 Above and behind this level is pavement
epithelium.

6.  Middle ear cavity lies between external and
inner ear.
 Has form of biconcave disc, measures
Vertical diameter- 15mm
 Antero-posterior diameter- 13mm
 Transverse diameter-very narrow
 - 6mm upper part
⁻ 2mm center
⁻ 4mm lower part

7. 6mm
4mm
2mm
15mm

10. Walls and its contents

11.  partly Bony and membranous.
 Bony part: Squamous part of temporal bone
 : BONY LATERAL WALL OF THE
EPITYMPANUM
: CENTRALLY BY TYMPANIC
MEMBRANE
: BONY LATERAL WALL OF
HYPOTYMPANUM
Accordingly cavity is divided into three parts-

12. .

13. ◦ Mesotympanum:
 situated medial to the pars tensa of tympanic
membrane.
 Anterior mesotympanum is lined by columnar ciliated
epithelium, posterior by pavement epithelium.
◦ Hypotympanum:
 situated below the level of tympanic membrane.
 Lined by ciliated columnar epithelium.

14.  provides
communication
between antrum and
rest of tympanic
cavity.
 Superior border of
attic is tegmen
tympani, which is a
thin wall, at times
dehiscent.
 Divided into medial
and lateral parts , by
head of malleus and
body of incus.
 Medial larger than
lateral.

16.  Medial attic communicates with
mesotympanum through opening called
isthmus tympani
 Isthmus tympani is a narrow , elongated
space divided by long process of incus into
anterior isthmus with tendon of tensor
tympani as anterior border.
 Posterior isthmus bounded by pyramidal
eminence and buttress at fossa incudis.

18.  Lateral attic located between
 the outer attic wall {scutum } -laterally .
 Malleus head and body incus- medially.
 Smaller due to two reasons-
 Outward projection of ossicles.
 Scutum runs obliquely medially from tegmen
tympani to the upper edge of bony annulus.

19.  The lateral
epitympanic wall is
wedge shaped and is
directed laterally. Its
lower part is called
the “scutum” or the
outer attic wall.
{EASILY ERODED BY
CHOLESTEATOMA }

20.  Scutum:
◦ forms part of the superior deep portion of the
external meatus
◦ gives attachment to the pars flaccida , which is
the lateral wall of the Prussak’s space.
◦ first bony structure to be eroded by attic
cholesteatoma secondary to a retraction pocket
leaving a tell tale sign on HRCT temporal bone.

21.  Openings in medial surface of lateral wall
◦ Posterior canaliculus for chorda tympani.
◦ Petrotympanic / Glaserian fissure
◦ Canal of Huguier

23.  Posterior canaliculus :
 Chorda tympani Branch of facial nerve .
 origin may vary
 Enters tympanic cavity from posterior canaliculus at
junction of lateral and posterior walls
 Runs across medial surface of TM .
 Passes medial to upper portion of handle of malleus
above tendon of TT
 Leave by anterior canaliculus(canal of Huguier)
 Supplies taste sensation to anterior 2/3rd of tongue
and secretomotor fibres to submandibular gland
 This canal also contains a branch from the
stylomastoid artery

24.  Petrotympanic (Glaserian) fissure :
◦ Opens anteriorly
◦ Slit measuring about 2mm receives the anterior
malleal ligament and transmits anterior tympanic
branch of maxillary artery
 Canal of Huguier:
It lies medial to the Glaserian fissure. The chorda
tympani nerve leaves through this.

27.  Elliptical disc stretched obliquely.
 Convex towards tympanic cavity
 Maximum convexity is called umbo
 Longest diameter: 9-10mm-
 thickness 0.1mm
 Makes an angle of 55o
with the floor of the
meatus.
 Parts: Pars flaccida and
Pars tensa

28.  The greater part formed by pars tensa ,wh
thickened peripherally into
fibrocartilagenous annulus
 which fits into grooved tympanic sulcus,
ring like groove in the tympanic ring.
 The tympanic ring is deficient superiorly -
notch of Rivinus .
 The pars flaccida inserts directly on this
notch, and due to the absence of sulcus and
the tympanic ring,
 the pars flaccida is lax rendering it more
predisposed to a retraction

29.  Layers:
 Outer epithelial
 Middle fibrous-in pars tensa -radial and
circular fibers but not much in pars flaccida
 Inner mucosal
 Two folds arises from the notch of rivinus to
the lat surface of malleus known as ant &
post malleolar folds

31. Inner surface of the tympanic
membrane:
◦ The TM is supplied by a
vascular circle formed by the
1. anterior tympanic artery
branch from IMA
2.Posterior tympanic artery
from the stylomastoid
branch of the posterior
auricular artery.
1. .

32. 3.Tubal twig from
ascending pharyngeal
anastomosis
4.Arteria nutrica malleo-
incudei twig from middle
meningeal artery-
sharpnells membrane
Outer surface of the
tympanic membrane:
1. Arteria manubrii having
uncertain origin.
2. eep auricular artery

33.  The membrane receives its innervations from
the auriculotemporal branch of the (CN V) ,
and the auricular branch of the vagus (CN X)
arnolds nerve/aldermans nerve.
Venous drainage
 external jugular
 Transverse sinus
 Dural veins

34.  Tegmen tympani.
 Formed by petrous part & squamous part of
temporal bone and petrosquamous suture line.
 Transmits venous drainage into superior
petrosal sinus.
SEPERATES MIDDLE EAR FROM MIDDLE
CRANIAL FOSSA.
 {PETROSQUAMOUS SUTURE LINE IN CHILDREN IS
NOT COMPLETELY CLOSED SO FORMS A ROUTE
FOR INFECTION TO SPREAD INTO EXTRADURAL
SPACE }

35.  Thin bone separating it from jugular bulb.
 Entirely formed by the petrous part.
 It is thin in newborns and thickens with age.
 May be deficient in some patients.
 The inferior tympanic canaliculus, which
transmits the Jacobson’s nerve

36. Anterior
Roof
Floor
Posterior

37.  Narrow- medial and lateral walls converge
 Divided into upper and lower portion
 Lower portion: -Thin bone separating middle ear
cavity from carotid artery.
Perforated by superior and inferior carotico
tympanic nerves, it is through these nerves
sympathetic nerves reach tympanic plexus.
 Upper portion: Two tunnels:
 Lower tunnel transmits bony portion of
Eustachian tube.
 Upper tunnel transmits tensor tympani
muscle (semi tunnel).
UPPER THIRD HAS ANTERIOR EPITYMPANIC SINUS WHICH
IS PEUMATISED.
{RESIDUAL CHOLESTEATOMA IN CANALWALL UP SURGERY }

39.  Named by Bartolomeus Eustachius
 Channel which connects middle ear with
nasopharynx .
 36mm long.
 Lateral 1/3 is bony
 Medial 2/3 is cartilagenous
 Isthmus : Narrowest part of ET b/w bony
and cartilagenous - 0.5MM

40.  Lenght12 mm , Laterally opens into anterior
wall of tympanic membrane.
 5X2mm ,Oval shaped,widest part of ET.
 Runs b/w tympanic plate and petrous part
of temporal bone.
 RELATIONS :
Superiorly –Bony roof seperating from
tensor tympani
Medially- Carotid canal
 Takes descending diagonal course at angle
of 40 degree from horizontal

41.  CARTILAGINOUS PART : 24MM
 Made up of fibrocartilagenous skeleton and
muscles.
 Passess downward froward and medially toward
nasopharyngeal orifice making angle of 160
degree with bony part.
 J shaped .
 On cross section-Shepherds crook ,cartilage
confined to upper and medial part.
 FIXED TO SKULL BASE THROUGH A GROOVE WHICH
IS PRESENT B/W PETROUS PART OF TEMPORAL BONE
AND GREATER WING OF SPHENOID .

42.  PHARYNEAL END : Vertically slit like , 1-1.25 CM
behind below posterior end of inferior turbinate.
TORUS TUBARIS : Cartilagenous part of pharyngeal
opening is raised to form a elevation.
FOSSA OF ROSENMULLER :pharyngeal recess behind
torus.

43.  TENSOR PALATI :arises from
 Scaphoid fossa
 Spine of sphenoid
 Along whole length of tubal cartilage
 It decends ,converges and turns medially
around the pterygoid hamulus and spread into
soft palate.
 Aka DILATOR TUBE muscle – help in opening ET .
 Normally ET is closed –opened by swallowing
and yawing by action of tensor palati and
sphincter of nasopharyngeal isthmus
 Supplied by MANDIBULAR NERVE.

44.  LEVATOR PALATI ; Arise from the base of
petrous bone and passes under the floor of
tube, inserted directly into soft palate and
meets its fellow of opposite side
 PHARYNGEAL PLEXUS .
 MUCOSA OF ET :
 Cartilaginous part- Respiratory ciliated
columnar epithelium with goblet cells .
 Bony part- the cilia n goblet cells decrease
in number

45.  The medial wall separates the middle ear
from the inner ear.
 1.Promontory
 2.Oval window
 3.Round window niche
 4.Facial nerve canal
 5.processus
cochleariformis

46.  The most prominent portion.
 Rounded projection occupying most of
central portion of the medial wall .
 Projection is by the underlying basal turn of
the cochlea.
 The promontory has numerous small
grooves on its surface.
 These grooves contain the tympanic plexus of
nerves

47. Divides medial wall into 2 parts:
◦ The inferior part is opposite the deep orifice of the
external auditory canal and is directly explorable
through this canal
◦ The superior part is opposite the bony lateral wall
of the tympanic cavity.

48.  Behind and above the promontory is the oval
window.
 Kidney shaped opening connecting the
tympanic cavity with the vestibule.
 Closed by stapes foot plate and its annular
ligament.
 The long axis of the fenestra vestibuli is
horizontal.
 3.25mm long and 1.75 mm wide.
 Above this is the canal for facial nerve
(horizontal portion) and below lies the
promontory.

51.  Found in a triangular niche with anterior,
posterosuperior and posteroinferior border.
 Covered by secondary tympanic membrane
 The secondary tympanic membrane appears
to be divided into an anterior and posterior
portions by the presence of a transverse
thickening
 It is made up of three layers;
 the outer mucosal,
 middle fibrous and an
 inner endothelial layer.

52.  The membrane of the fenestra cochleae does
not lie at the end of the scala tympani but
forms part of its floor.
 The round window faces inferiorly and a little
posteriorly, lying completely under the cover
of the promontory and hence usually is
difficult to visualise.
 Measures 2.3×1.9 mm and is placed right
angle to the oval window

53.  The ampulla of the PSCC is the closest
vestibular structure to this membrane.
 The nerve supplying the ampulla of the PSCC
(singular nerve) lies close to this membrane.
 Hence forms a landmark for the singular
nerve.
 This is useful during surgical procedures like
singular neurectomy for treatment of
intractable vertigo.
Round window ctnd….

54.  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

55. facial canal which runs above the promontary
& oval window .
FACIAL CANAL

56.  A bony projection .
 Tensor tympani tendon passess through it
as it turns laterally .
 Above the processus cochleariformis there
is a small bulge in facial canal which marks
the geniculate ganglion
 greater suprficial petrosal nerve runs in a
bony canal.

58.  The posterior wall can be divided into two
distinct parts:
◦ The upper third-corresponds to the aditus
ad antrum ;represents the posterior limit of
the epitympanum
◦ The lower two thirds - correspond to the
posterior wall of the retrotympanum.

59.  The pyramidal eminence
◦ The pyramidal eminence is situated at the center of
the posterior wall immediately behind the oval
window; it is about 2 mm height.
◦ It lodges the body of the stapedial muscle and its
apex gives passage to the stapedial tendon.
◦ The pyramidal eminence communicates with the
facial bony canal by a minute aperture which
transmits the stapedial branch of the facial nerve.
 The chordal eminence:
◦ The chordal eminence is situated lateral to the
pyramidal eminence and 1 mm medial to the
tympanic membrane..

60.  The styloid eminence
◦ The styloid eminence or Politzer eminence is a
recognized smoothed elevation at the inferior part
of the posterior wall; it represents the base of the
styloid process.

61.  chordal ridge of Proctor
◦ The chordal ridge runs laterally and transversally
from the pyramidal eminence to fuse with the chordal
eminence.
 pyramidal ridge
◦ The pyramidal ridge is very prominent. It runs
inferiorly from the base of the pyramidal eminence to
the styloid eminence. It could be absent.
 styloid ridge
◦ The styloid ridge connects the styloid prominence to
the chordal eminence.
 ponticulus
 subiculum

63.  Aditus: aditus ad antrum connects middle ear
space with mastoid antrum.
 Dimension 4 × 4 × 4 mm
 Fossa incudis: lodges short process of incus
and posterior ligament.
 Pyramid: contains stapedius muscle.
 Recess:
 Facial recess
 Sinus tympani

64.  Facial recess (suprapyramidal recess):
 lies lateral to facial nerve.
MEDIALLY : FACIAL NERVE
LATERALLY : TYMPANIC ANNULAS
CHORDA TYMPANI RUNS B/W THESE.
 Sinus tympani (infrapyramidal recess):
 the niche of two labyrinthine
 windows communicate posteriorly
 with this deep recess
 RELATIONS
SUPERIORLY : PONTICULUS
INFERIORLY : SUBICULUM
LATERAL : MASTOID SEGMENT OF FACIAL
NERVE
MEDIAL : POSTERIOR SEMICIRCULAR CANAL
{ CHOLESTEATOMA NIDUS CAN BE HERE CAUSING RECCURANCe

66.  Three bones: Auditory ossicles derive names from
the Blacksmiths forge
◦ Malleus
◦ Incus
◦ Stapes
 Two muscles:
◦ Tensor tympani
◦ Stapedius
 Two nerves:
◦ Tympanic plexus
◦ Chorda tympani

69. Hammer shaped ,largest -9mm
20-25mg wt
 1ST Arch derivative
 PARTS – Head
neck
anterior and lateral process,
handle or manubrium.
 HEAD – saddle shaped facet on posteriormedial
surface which articulates with body of incus.
 Lies in attic region

70.  This articular surface is constricted near its
middle dividing the articular facet into a
larger superior and a smaller inferior
portions.
 The inferior portion of the articular facet lies
at right angles to that of the superior portion.
 This projecting lower portion is also known
as the cog or spur of the malleus.
 LATERAL PROCESS :important landmark in tympanic
membrane ,receive anterior and posterior folds

72.  The neck is narrow and flattened portion.
 Medial surface gives attachment to the tensor
tympani
 Chorda tympani crosses its medial surface above
the tensor thmpani tendon but below neck
{SO AMPUTATION OF HEAD DOESN’T AFFECT
CHORDA TYMPANI OR TENSOR TYMPANI }
 Handle directed medially and posteriorly to form
the umbo.
 Anterior and lateral process.
 Attachments:
◦ The anterior suspensory ligament
◦ The lateral suspensory ligament
◦ The superior suspensory ligament
◦ The anterior malleal ligament
◦ The posterior malleal ligament

73. SML
TT TENDON

74.  1ST ARCH DERIVATIVE resembles bicuspid tooth
 Measures 6 6 mm
 weighs about 30 mg.
 It has a trapezoidal body with short process, long
process, and a rounded lenticular process.
 Both body and short process are in attic.
 The lenticular process connects the long process
with the head of stapes.

76.  Ligaments of the Incus:
◦ The posterior incudal ligament
◦ The superior incudal ligament.

77.  1ST BONE TO UNDER GO EROSION LONG
PROCESS due to precarious blood supply.
 BODY is in epitympanum suspended by
superior incudal ligament from tegmen
tympani.
 SHORT PROCESS : Projects backwards from
the body to lie in the fossa incudis in
posterior wall by short suspensory
ligament.

78.  Smallest ossicle
 Stirrup shaped
 2ND ARCH DERIVATIVE
 PARTS : HEAD , NECK , ANTERIOR AND
POSTERIOR CRURA AND FOOTPLATE.
 HEAD : points laterally and has a cartilage
covered area facet for articulation with
lenticular process of incus.
 The tendon of stapedius muscle is attached to
the posterior part neck of stapes and posterior
part of posterior crura.

79.  CRURA : arises from lower part of neck
anterior is thinner and less curved than
posterior
 both are hollow on concave surface, both
crura join foot plate which cover oval
window.
 FOOTPLATE : Superior margin is convex and
inferior margin is straight lies over the oval
window by annular ligament.
 Measure 3.25X1.75MM

80.  INCUDOMALLEOLAR JOINT – SADDLE JOINT.
 INCUDOSTAPEDIAL JOINT – BALL & SOCKET
JOINT.

82.  Stapedius:
 Origin from walls of
the conical cavity
within the pyramid.
 A slender tendon
emerges from the
apex of the pyramid.
 Insertion over the
post part of neck and
upper portion of post
crus
 Supplied by small
branch of facial nerve

83.  On contraction this muscle rocks the stapes
backwards holding it firm against the annular
ligament preventing excessive transmission of
sound into the inner ear.
 Patients with facial nerve palsy have hyperacusis
because of lack of action of this muscle.

84.  Origin :wall of bony canal above eustachain
tube, greater wing of sphenoid
 Passes backward into tympanic cavity,along
medial wall little below facial nerve
 Enters processus cochlearformis , turns at
right angles inserting into the medial aspect
of the upper end of the handle of the malleus
 Supplied by mandibular nerve via branch
from medial pterygoid nerve

85.  This muscle tenses
the tympanic
membrane by
holding the handle
of the malleus thus
helping the middle
ear in better sound
perception.

86.  Chorda tympani.
◦ Branch of facial nerve. Origin may vary.
◦ Enters tympanic cavity from the posterior canaliculus
at junction of lateral and posterior wall
◦ Runs across medial surface of TM
◦ Passes medial to upper portion of handle of malleus
above tendon of Tensor tympani.
◦ Leave by way of anterior canaliculus(canal of Huguier)
◦ Supplies taste sensation to anterior 2/3rd of tongue
and secretomotor fibres to submandibular gland.

87.  Over promontory
 Formed by Tympanic branch of 9th nerve,also
called Jacobson’s nerve
 Caroticotympanic nerves{supplies the
sympathetic component. }
 Supplies mucous membrane lining tympanic
cavity ,ET and mastoid antrum and cells
 Also provide branches to greater and lesser
superficial petrosal nerves

88.  1.ANTERIOR TYMPANIC : Branch of maxillary
artery supplies :
 TM , Malleus,incus,anterior part of tympanic
cavity.
 2.STYLOMASTOID : Branch of posterior
auricular artery
: Stapedius muscle,posterior part of tympanic
membrane.
 3.MASTOID : branch of Stylomastoid artery
: Mastoid air cells
 4.PETROSAL : branch of middle meningeal
artery
: Roof of mastoid ,roof of epitympanum

89.  5.SUPERIOR TYMPANIC : middle meningeal
artery : malleus , incus , tensor tympani
 6.INFERIOR TYMPANIC : ascending
pharyngeal artery : mesotympanum
 7.BRANCH FROM ARTERY OF PTERYGOID
CANAL : meso n hypotympanum .
 8.TYMPANIC ARCHES FROM INTERNAL
CAROTID
: meso n hypotmpanum

93.  Communicates with middle ear via the
aditus.
 Antrum is well defined at birth.
 Measurements:
◦ Volume: 1ml
◦ Antero-posterior diameter: 14mm
◦ Vertical diameter: 9mm
◦ Transverse diameter: 7mm

94.  Medial wall: Posterior semicircular canal and
more deeply to posterior cranial fossa and
endolymphatic sac
 Roof: Middle cranial fossa
 Posterior wall: sigmoid sinus
 Lateral wall: Thickness at birth 2mm, adult
life 12-15mm, corresponds to
suprameatal/Macewen’s triangle.
 Floor: digatric muscle laterally and sigmoid
sinus medially.
 Mucosa : Flatenned nonciliated epithelium
without goblet cells or mucous glands.