The middle ear is located in the petrous portion of the temporal bone. It contains the three auditory ossicles (malleus, incus, stapes), two small muscles (tensor tympani and stapedius), nerves, and air. It connects the external ear canal to the inner ear and contains important structures like the Eustachian tube. The middle ear transmits sound vibrations from the tympanic membrane to the inner ear through the ossicles while also containing muscles that help dampen vibrations.

1. Middle ear
Dr M Idris Siddiqui
External Ear
Middle Ear
Internal Ear

2. Middle ear
(tympanic cavity or tympanum)
• It lies in petrous part of temporal bone.
• Small biconcave box like RBC set on its edge.
• Vertical axis is roughly parallel to plane of ear
drum.
• Filled with air, lined by mucus membrane.
• Connected in front with nasopharynx &
behind with tympanic (mastoid) antrum

4. The Middle Ear
• This part of the ear is in a narrow cavity in the
petrous part of the temporal bone.
• It contains
– Air ,
– Three auditory ossicles,
– A nerve and
– Two small muscles.
• The middle ear is separated from the external
acoustic meatus by the tympanic membrane.
• This cavity includes the tympanic cavity proper, the
space directly internal to the tympanic membrane,
and the epitympanic recess, the space superior to it.
• Posterosuperiorly, the tympanic cavity connects with
the mastoid cells through the aditus ad antrum (mastoid
antrum).

5. Contents Remarks
1 3 ear ossicles  Malleus
 Incus
 Stapes
2 Ligaments of ear ossicles
There are three for the malleus and one each for the incus and stapes.
The anterior ligament of the malleus
The lateral ligament of the malleus.
The superior ligament of the malleus
The posterior ligament of the incus
The anular ligament of the base of
the stapes
3 2 Muscles Tensor tympani
Stapedius
4 Vessles supplying & draining middle ear
5 Nerves Chorda tympani
tympanic plexus
6 Air
Contents of middle ear cavity
The middle ear is lined by mucous membrain

7. Boundaries of middle ear
• Lateral wall or membraneous wall:
– Formed by Tympanic Membrane and squamous portion of Temporal Bone.
• Medial wall or labyrinthine wall:
– Promontory (Outer wall of inner ear)&(oval and round windows, prominence of
facial nerve)
• Anterior wall or carotid wall
– (Opening of Eustachian Tube and tendon of tensor tympani)
• Posterior wall or mastoid wall
– (Tympanic aditus to mastoid cells, fossa incudis, pyramidal prominence, facial
nerve through tympanic sulcus)
• Inferior wall or jugular wall
– (Tympanic plate of Temporal Bone separating it from internal jugular vein)
• Superior wall or tegmental wall
– (Tegmen tympani, continuing posteriorly to tympanic atrium)

10. The Roof or Tegmental Wall
• This is formed by a thin plate of
bone, called the tegmen tympani
(L. tegmen, roof).
• It separates the tympanic cavity
from the dura on the floor of middle
cranial fossa.
• The tegmen tympani also covers the
aditus ad antrum.

12. The Floor or Jugular Wall
• This wall is thicker than the roof.
• It separates the tympanic cavity from the
superior bulb of the internal jugular vein. The
internal jugular vein(posterior) and the internal
carotid artery(anterior) diverge at the floor of
the tympanic cavity.
• The tympanic nerve, a branch of the
glossopharyngeal nerve (CN IX), passes
through an aperture in the floor of the
tympanic cavity and its branches form the
tympanic plexus.

14. The Lateral or Membranous Wall
• This is formed almost entirely by the tympanic
membrane, bone above & bone below.
• Superiorly it is formed by the lateral bony wall
of the epitympanic recess.
• The uppermost part of middle ear is called epitympanum
or attic.
• The handle of the malleus is incorporated in the
tympanic membrane, and its head extends into
the epitympanic recess.
• Chorda tympani passes across ear drum & handle of
malleus. It enters middle ear cavity at canacullus of chorda
tympani in posterior wall.

17. Inferior salivary nucleus
9th n.
Tympanic branch
Tympanic plexus
in middle ear
Lesser petrosal
nerve
Otic ganglion
Auriculotemporal
nerve
Parotid
gland

18. Tympanic plexus
Syn: plexus tympanicus [NA], Jacobson's plexus.
• A plexus on the promontory of the
labyrinthine wall of the tympanic cavity,
formed by
–The tympanic nerve,
–An anastomotic branch of the facial, and
–Sympathetic branches from the internal carotid
plexus; (The caroticotympanic nerves, the
superior and inferior caroticotympanic nerves )
• It supplies the mucosa of the middle ear,
mastoid cells, and auditory (eustachian) tube,
and gives off the lesser superficial petrosal
nerve to the otic ganglion.

19. Tympanic nerve or Jacobson nerve
• Jacobson nerve is the tympanic branch of
the glossopharyngeal nerve (CN IX) and arises from
the inferior ganglion of the glossopharyngeal nerve.
It also carries preganglionic parasympathetic fibres,
from the inferior salivary nucleus, which eventually
enter the otic ganglion.
• Jacobson nerve enters the tympanic cavity via
the inferior tympanic canaliculus and contributes to
the tympanic plexus located on the cochlear
promontory. The parasympathetic fibres leave the
plexus as the lesser petrosal nerve

21. • It may be regarded as the continuation of the
tympanic branch of the glossopharyngeal nerve,
traverses the tympanic plexus.
• It occupies a small canal below that for tensor
tympani. It runs past, and receives a connecting
branch from, the geniculate ganglion of the facial
nerve.
• The lesser petrosal nerve emerges from the anterior
surface of the temporal bone via a small opening
lateral to the hiatus for the greater petrosal nerve
and then traverses the foramen ovale or the small
canaliculus innominatus to join the otic ganglion.
Postganglionic secretomotor fibres leave this
ganglion in the auriculotemporal nerve to supply
the parotid gland.
The lesser petrosal nerve

24. The Medial or Labyrinthine Wall
• This separates the middle ear from the membranous labyrinth
(semicircular ducts and cochlear duct) encased in the bony
labyrinth.
• The medial wall of the tympanic cavity exhibits several
important features.
• Centrally, opposite the tympanic membrane, there is a rounded
promontory (L. eminence) formed by the first turn of the cochlea.
• The tympanic plexus of nerves, lying on the promontory, is formed by
fibres of the facial and glossopharyngeal nerves.
• The medial wall of the tympanic cavity also has two small
apertures or windows.
• The fenestra vestibuli (oval window) is closed by the base of the
stapes, which is bound to its margins by an annular ligament,
above & behind the promontry. Through this window, vibrations
of the stapes are transmitted to the perilymph window within
the bony labyrinth of the inner ear.
• The fenestra cochleae (round window) is inferior to the fenestra
vestibuli, below & behind the promontry.This is closed by a
second tympanic membrane.
• A rounded ridge formed by horizontal plate of facial nerve arches above promontery &
oval window.
• Sinus tympani: a depression between two windows.

26. The Posterior or Mastoid Wall
• This wall has several openings in it.
• In its superior part is the aditus , which leads posteriorly from the
epitympanic recess to the mastoid cells.
• Anterior to aditus there is posterior wall of epitympanic recess. On
it there is a depression “fossa incudis” tip of incus arises from
here.
• Inferiorly is a pinpoint aperture on the apex of a tiny, hollow
projection of bone, called the pyramidal eminence (pyramid). This
eminence contains the stapedius muscle.
Its aperture transmits the tendon of the stapedius, which enters
the tympanic cavity and inserts into the stapes.
• Medial to aditus there is vertical part of facial nerve descending to
end at stylomastoid foramen.
• Lateral to the pyramid, there is an aperture (posterior
canaliculus)through which the chorda tympani nerve, a branch of the
facial nerve (CN VII), enters the tympanic cavity.

27. The Anterior Wall or Carotid Wall
• This wall is a narrow as the medial and lateral walls
converge anteriorly.
• There are two openings in the anterior wall.
• The superior opening communicates with a canal
occupied by the tensor tympani muscle in upper part of wall.Its
tendon inserts into the handle of the malleus and keeps the
tympanic membrane tense.
• In middle part, Inferiorly, the tympanic cavity
communicates with the nasopharynx through the auditory
tube.
• In lower part, a plate of bone separating middle ear
from internal carotid artey in crotid canal.
• The bony septum between semicanal for tensor
tympaniis continued posteriorly on medial wall of
middle ear as a shelf processus cochlariformis. The
posterior edge of it forms a pulley around which tendon
of tensor tympani turns latrally at 90 to run to malleus.
•

31. Muscles Moving the Auditory Ossicles
• The Tensor Tympani Muscle:
• This muscle is about 2 cm long.
• Origin: superior surface of the cartilaginous part of the auditory tube, the
greater wing of the sphenoid bone, and the petrous part of the temporal bone.
• Insertion: handle of the malleus.
• Innervation: mandibular nerve (CN V3) through the nerve to medial pterygoid.
• The tensor tympani muscle pulls the handle of the malleus medially, tensing
the tympanic membrane, and reducing the amplitude of its oscillations.
• This tends to prevent damage to the internal ear when one is exposed to load
sounds.
•
• The Stapedius Muscle:
• This tiny muscle is in the pyramidal eminence or the pyramid.
• Origin: pyramidal eminence on the posterior wall of the tympanic cavity. Its
tendon enters the tympanic cavity by traversing a pinpoint foramen in the apex
of the pyramid.
• Insertion: neck of the stapes.
• Innervation: nerve to the stapedius muscle, which arises from the facial nerve
(CN VII).
• The stapedius muscle pulls the stapes posteriorly and tilts its base in the
fenestra vestibuli or oval window, thereby tightening the anular ligament and
reducing the oscillatory range.
• It also prevents excessive movement of the stapes.

32. The Auditory Ossicles
• The Malleus :
• Its superior part, the head, lies in the epitympanic recess.
• The head articulates with the incus.
• The neck, lies against the flaccid part of the tympanic membrane.
• The chorda tympani nerve crosses the medial surface of the neck of the
malleus.
• The handle of the malleus (L. hammer) is embedded in the tympanic
membrane and moves with it.
• The tendon of the tensor tympani muscle inserts into the handle.
•
• The Incus :
• Its large body lies in the epitympanic recess where it articulates with the head of
the malleus.
• The long process of the incus (L. an anvil) articulates with the stapes.
• The short process is connected by a ligament to the posterior wall of the
tympanic cavity.
•
• The Stapes:
• The base (footplate) of the stapes (L. a stirrup), the smallest ossicle, fits
into the fenestra vestibuli or oval window on the medial wall of the tympanic
cavity.

35. ARTICULATION OF AUDITORY OSSICLES
The articulations are typical synovial joints.
• The incudomalleolar joint is saddle
shaped.
• The incudostapedial joint is a ball and
socket articulation.
• Their articular surfaces are covered with articular cartilage,
and each joint is enveloped by a capsule rich in elastic
tissue and lined by synovial membrane

41. Functions of the Auditory Ossicles
• The auditory ossicles increase
the force but decrease the amplitude
of the vibrations transmitted
from the tympanic membrane.

45. The Auditory Tube
• This is a funnel-shaped tube connecting the nasopharynx
to the tympanic cavity.
• Its wide end is towards the nasopharynx, where it
opens posterior to the inferior meatus of the nasal
cavity.
• The auditory tube is 3.5 to 4 cm long; its posterior 1/3
is bony and the other 2/3 is cartilaginous.
• It bony part lies in a groove on the inferior aspect of
the base of the skull, between the petrous part of the
temporal bone and the greater wing of the sphenoid
bone.
• The pharyngotympanic tube is lined by mucous membrane that is
continuous posteriorly with that of the tympanic cavity and anteriorly
with that of the nasopharynx.
• The function of the auditory tube is to equalise pressure of
the middle ear with atmospheric pressure.

48. Relations of auditory tube
• Lateral:
– Tensor palati
• Medial :
– Leavator palati
• Inferior :
– Pharyngobasilar fascia
• Superior :
– Base of skull
• It enters nasopharynx by passing above supereior border of
superior constrictor at posterior border of medial pterygoid
plate

49. Cartilaginous Part  About 2-3 cm long, attached to med end of bony part
 Lies in a groove btw greater wing of sphenoid & apex of
petrous temporal
 superior& medior wall = cartilage
 lateal & inferior walls = fibrous mbm
Relations:
a. Anterolateral
1. tensor veli palatini
2. mandibular n
3. middle meningeal art
b. Posteromedial :
1. levator veli palatini
2. pharyngeal recess
Bony Part  About 1 cm long
 Lies in petrous temporal bone, near tympani plate
 lateral end is wider  opens into middle ear cavity
 Medial end is narrow (isthmus)  attach to cartilaginous part
Relations:
a. Superiorly: canal for tensor tympani
b. Anterolateal: tympanic portion of temporal bone
c. Posteromedial:carotid canal

50. • The arteries of the pharyngotympanic tube are
derived from the ascending pharyngeal artery, a
branch of the external carotid artery, and the
middle meningeal artery and artery of the pterygoid
canal, branches of the maxillary artery.
• The veins of the pharyngotympanic tube drain into
the pterygoid venous plexus. Lymphatic drainage of
the pharyngotympanic tube is to the deep cervical
lymph nodes.
• The nerves of the pharyngotympanic tube arise
from the tympanic plexus, which is formed by fibers
of the glossopharyngeal nerve (CN IX). Anteriorly,
the tube also receives fibers from the
pterygopalatine ganglion

51. Blockage of the Pharyngotympanic Tube
• The pharyngotympanic tube forms a route for an
infection to pass from the nasopharynx to the
tympanic cavity.
• This tube is easily blocked by swelling of its mucous
membrane, even as a result of mild infections (e.g.,
a cold), because the walls of its cartilaginous part
are normally already in apposition.
• When the pharyngotympanic tube is occluded,
residual air in the tympanic cavity is usually
absorbed into the mucosal blood vessels, resulting
in lower pressure in the tympanic cavity, retraction
of the tympanic membrane, and interference with
its free movement. Finally, hearing is affected.

52. The mastoid antrum
• It is a pea sized cavity in the mastoid process of the
temporal bone. The antrum (L. from G., cave), like the
tympanic cavity, is separated from the middle cranial fossa
by a thin plate of the temporal bone, called the tegmen
tympani.
• This structure forms the tegmental wall (roof) for the ear
cavities and is also part of the floor of the lateral part of the
middle cranial fossa.
• The antrum is the common cavity into which the mastoid
cells open. The antrum and mastoid cells are lined by
mucous membrane that is continuous with the lining of the
middle ear.
• Anteroinferiorly, the antrum is related to the canal for the
facial nerve.

54. Relations of masatoid antrum
• Anterior wall:
– Related to middle ear cavity, via aditus
• Posterior wall:
– Separates antrum from sigmoid sinus & cerebellum.
• Lateral wall:
– Forms forms floor of suprameatal triangle
• Superior wall:
– Tegmen tympani
• Inferior wall:
– Is perforated with holes through which antrum
communicates with mastoid air cells.
• Medial wall:
– Posterior semicircular canal.

55. Paralysis of the Stapedius
• The tympanic muscles have a protective action in
that they dampen large vibrations of the tympanic
membrane resulting from loud noises.
• Paralysis of the stapedius (e.g., resulting from a
lesion of the facial nerve) is associated with
excessive acuteness of hearing called hyperacusis or
hyperacusia.
• This condition results from uninhibited movements
of the stapes.

56. Otitis media
• Otitis media is a group of inflammatory diseases of the middle ear.
• The two main types are acute otitis media (AOM) and chronic
suppurative otitis media.
– Acute Otitis Media is an infection of abrupt onset that usually presents
with ear pain.
• There is bulging of tympanic membrane which is typical in a case of
acute otitis media.
• Chronic suppurative otitis media (CSOM) is a chronic inflammation
of the middle ear and mastoid cavity that is characterised by
discharge from the middle ear through a perforated tympanic
membrane.
• Symptoms: Ear pain, fever, hearing loss, ear discharge
• Causes: Viral, bacterial

57. Complications of Otitis Media
• Inadequate treatment of otitis media can result in the
spread of the infection into the mastoid antrum and
the mastoid air cells (acute mastoiditis).
• Acute mastoiditis may be followed by the further
spread of the organisms beyond the confines of the
middle ear. The meninges and the temporal lobe of the
brain lie superiorly.
• A spread of the infection in this direction could produce
a meningitis and a cerebral abscess in the temporal
lobe.
• Beyond the medial wall of the middle ear lie the facial
nerve and the internal ear. A spread of the infection in
this direction can cause a facial nerve palsy and
labyrinthitis with vertigo.
• The posterior wall of the mastoid antrum is related to
the sigmoid venous sinus. If the infection spreads in
this direction, a thrombosis in the sigmoid sinus may
well take place.

58. Otorrhea
Discharge from the ear can be caused by:
• Acute otitis media with perforation of the ear
drum.
• Chronic suppurative otitis media,
• Acute otitis externa.
• Trauma, such as a basilar skull fracture, can also
lead to discharge from the ear due to cerebral
spinal drainage from the brain and its covering
(meninges)