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Divided into:
 External (outer) ear
Consists of :
 Auricle or pinna
 External auditory
canal (external
auditory meatus,
external acoustic
meatus)
 Middle ear
 Internal ear
The Ear
Pinna
It is the outer expanded portion
of the ear, projects from the
side of the head
Serves to collect the vibrations
of the air by which sound is
produced
Consists of a thin plate of
elastic cartilage covered by
skin.
The skin is continuous with that
lining the external acoustic
meatus
Possesses both extrinsic and
intrinsic muscles, which are
supplied by the facial nerve
Helix
Antihelix
External auditory meatus
Tragus
Concha
Lobule
Auricular
muscles
Arteries :
 Posterior auricular artery, branch of the external
carotid artery
 Anterior auricular artery, branch of the superficial
temporal artery
 Auricular branch of the occipital artery.
Veins accompany the corresponding arteries.
Sensory nerves:
 Great auricular & Lesser occipital, from the cervical
plexus
 Auricular branch of the vagus nerve
 Auriculotemporal branch of the mandibular nerve
Motor nerves:
 Posterior auricular branch of facial nerve
External Auditory Meatus
Leads inward from the bottom
of the auricle to the tympanic
membrane (ear drum)
Conducts the vibrations to the
tympanic cavity.
About 4 cm. in length if
measured from the tragus
Forms an S-shaped curve, and
is directed:
 at first inward, forward, and
slightly upward
 it then passes inward and
backward
 lastly is carried inward, forward,
and slightly downward.
The floor and the anterior wall of the
meatus are longer than the roof and
the posterior wall, because the
tympanic membrane, which closes the
inner end of the meatus, is placed
obliquely
The canal is formed partly by cartilage
and partly by bone
 The outer ⅓ is formed of elastic
cartilage, that is continuous with
the cartilage of the auricule
 The medial ⅔ is bony, formed by
tympanic plate of the temporal
bone.
It is an oval cylindrical canal, narrower
in the bony portion and presents two
constrictions:
 one near the inner end of the
cartilaginous portion
 another in the osseous (bony)
portion
It is lined by thin skin that
adheres closely to the
underlying cartilage and the
bone, and also covers the
outer surface of the tympanic
membrane
Its outer third is provided with
hairs and sebaceous and
ceruminous (modified sweat)
glands that secrete a
yellowish brown wax.
The hairs and the wax
provide a sticky barrier that
prevents the entrance of
foreign bodies.
Arteries: Supplied by the branches of the:
 Posterior auricular artery
 Maxillary artery
 Superficial temporal artery
Veins: Accompany the corresponding arteries
Nerves: Are chiefly derived from the:
 Auriculotemporal branch of the mandibular nerve
 Auricular branch of the vagus nerve
Lymphatics: Drain into the:
 Superficial parotid lymph nodes
 Mastoid lymph nodes
 Superficial cervical lymph nodes
Tympanic Membrane (Ear Drum)
Separates the external acoustic
meatus from the middle ear
(tympanic) cavity.
It is a thin, semitransparent
membrane, nearly oval in form,
slightly broader above than below
It is directed obliquely downward,
forward and laterally, & form an
angle of about 55˚ with the floor of
the meatus.
Its longest diameter measures from
9 to 10 mm & its shortest diameter
measures from 8 to 9 mm.
The handle of the malleus is
firmly attached to the medial
surface of the membrane as
far as its center, which it draws
toward the tympanic cavity
The lateral surface of the
membrane is thus concave,
and the most depressed part
of this concavity is named the
umbo (produced by the tip of
the handle of malleus)
When the tympanic membrane
is illuminated through an
otoscope, the concavity
produces a cone of light that
radiates anteriorly and
inferiorly from the umbo
It is three-layered structure consisting of
thin skin laterally, mucosa medially, and
an intervening fibrous layer.
The fibrous layer thickens along the
circumference to form the annulus, an
incomplete ring which is fixed into a
groove, the tympanic sulcus in the
bone at the inner end of the meatus
The tympanic sulcus is deficient
superiorly, which forms a notch
From the sides of the notch, anterior &
posterior malleolar folds pass to the
lateral process of maleus
Superior to the malleolar folds the small
triangular area of the membrane is
known as the pars flaccida. The
remainder of the membrane forms the
pars tensa
Arteries: derived from the branches of the:
 Maxillary artery
 Posterior auricular artery
Veins:
 The superficial veins open into the external jugular vein
 Those on the deep surface drain partly into the transverse
sinus and veins of the dura mater, and partly into a plexus
on the auditory tube.
Nerve supply: The tympanic membrane is extremely
sensitive to pain and receives its nerve supply:
 On the outer surface by the:
 Auriculotemporal nerve
 Auricular branch of the vagus nerve
 On the mucosal surface by the:
 Tympanic branch of the glossopharyngeal nerve
Middle Ear (Tympanic) Cavity
An irregular, slitlike, laterally
compressed space within the
petrous part of the temporal bone.
Long axis lies parallel to the plane
of the tympanic membrane
Normally sealed laterally by the
tympanic membrane
Lined with mucous membrane
Filled with air, which is conveyed
to it from the pharynx through the
auditory tube
Contains a chain of movable
bones, the ossicles
Communicates:
 Posteriorly: with the mastoid air
cells through the mastoid
antrum
 Anteriorly: with the nasopharynx
through the auditory tube
Consists of two parts:
 Tympanic cavity proper, lies
opposite the tympanic
membrane
 Attic or Epitympanic recess, lies
above the level of the
membrane; contains the upper
half of the malleus and the
greater part of the incus &
communicates with the mastoid
antrum via the aditus
Tympanic Cavity cont’d
It is a six-sided
cavity and has a:






Roof
Floor
Lateral wall
Medial wall
Anterior wall
Posterior wall
Roof (Tegmental Wall):
 Formed by a thin plate of
bone, the tegmen tympani,
part of the petrous
temporal bone.
 Separates the tympanic
cavity from the cranial cavity.
Floor (Jugular Wall):
 Is narrow, formed by a thin
plate of bone (sometimes
just fibrous tissue)
 Separates the tympanic
cavity from the superior
bulb of the internal jugular
vein in the jugular fossa
Lateral (Membranous) Wall:
 Formed mainly by the tympanic
membrane
 Partly by the ring of bone into
which this membrane is
inserted.
Medial (Labyrinthic) Wall:
 Vertical in direction, formed by
the lateral wall of the inner ear
 Presents the following features:
Promontory
Fenestræ vestibuli
Fenestra cochleæ
Prominence of the facial
canal.
Promontory
Rounded hollow prominence
Formed by the projection
outward of the first turn of the
cochlea
Furrowed on its surface by small
grooves, for the lodgment of
branches of the tympanic
plexus.
Fenestra vestibuli (oval
window)
An oval opening located above
and behind the promontory
Closed by the base of stapes
Deep to the window lies the
perilymph in the scala vestibuli
of the internal ear
Fenestra cochleae (round
window)
Situated below and a little behind
the promontory
Leads into the blind end of the
scala tympani of the internal ear
In the fresh state, closed by the
secondary tympanic membrane
Prominence of the facial
canal
Lies horizontally above the
fenestra vestibuli, and behind that
opening curves nearly vertically
downward along the posterior wall
Indicates the position of the bony
canal containing the facial nerve
Posterior (Mastoid) wall
 Wider above where it
shows a large irregular
aperture, the aditus, which
leads backward from the
epitympanic recess into
the tympanic or mastoid
antrum
 Below it is a small, hollow,
conical projection called
the pyramid, that contains
the stapedius muscle; its
summit projects forward
toward the fenestra
vestibuli, and is pierced by
a small aperture which
transmits the tendon of the
muscle.
Anterior (Carotid) Wall:
 Wider above than below
 In the lower part, formed
by a thin plate of bone
that separates the cavity
from the internal carotid
artery
 The upper part shows two
orifices:
 Upper small orifice is
the opening of the
canal for the tensor
tympani muscle
 Lower larger opening
is the tympanic orifice
of the auditory canal.
 The two canals are separated
from each other by a thin
horizontal plate of bone,
which passes backward on
the medial wall above the
promontory and fenestra
vestibuli.
 It supports the tensor tympani
muscle, and terminates there
by curving upward to form a
pulley, the processus
cochleariformis, over which
the tendon of the tensor
tympani muscle bends
laterally to reach its insertion
on the handle of the malleus
Ossicles
The smallest bones in the
body, three in number, linked
to each other
Lie in the tympanic cavity
Convert the sound waves
striking the eardrum into
mechanical vibrations and
then convey the vibrations
across the cavity to the
internal ear.
From lateral to medial, these
are the:
 Malleus
 Incus
 Stapes
Malleus





The largest ossicle, possesses a head,
a neck, a long process or handle, an
anterior process, and a lateral process.
Head: rounded, articulates posteriorly
with the incus.
Neck : constricted part below the head.
Handle: passes downward and
backward and is firmly attached to the
medial surface of the tympanic
membrane. It can be seen through the
tympanic membrane on otoscopic
examination.
Anterior process: a spicule of bone,
connected to the anterior wall of the
tympanic cavity by a ligament.
Lateral process: projects laterally, is
attached to the anterior and posterior
malleolar folds of the tympanic
membrane.
Incus
The incus possesses a large body
and two processes
 Body: rounded and articulates
anteriorly with the head of the
malleus
 Long process descends behind and
parallel to the handle of the malleus.
Its lower end bends medially and
articulates with the head of the
stapes. Its shadow on the tympanic
membrane can sometimes be
recognized on otoscopic
examination
 Short process projects backward
and is attached to the posterior wall
of the tympanic cavity by a ligament
Stapes




The stapes has a head, a neck, two
limbs, and a base
The head is small and articulates
with the long process of the incus
The neck is narrow and receives
the insertion of the stapedius
muscle
The two limbs (crura) diverge from
the neck and are attached to the
oval base.
The edge of the base is attached to
the margin of the fenestra vestibuli
by a ring of fibrous tissue, the
annular ligament
Muscles of the Ossicles
Tensor tympani
 Origin: Wall of auditory tube and
wall of its own canal
 Insertion: Handle of malleus
 Nerve Supply: Mandibular
division of trigeminal nerve
 Action: Dampens down
vibrations of tympanic
membrane
Stapedius
 Origin: Pyramid (bony projection
on posterior wall of middle ear)
 Insertion: Neck of stapes
 Nerve Supply: Facial nerve
 Action: Dampens down
vibrations of stapes
Nerves in the Tympanic Cavity
Facial nerve (intrapetrous
part)
Chorda tympani, branch of
facial nerve
Greater petrosal nerve,
branch of facial nerve
Tympanic nerve, branch of
glossopharyngeal nerve
Tympanic plexus
Lesser petrosal nerve
(parasympathetic)
Deep petrosal nerve
(sympathetic)
Facial Nerve
Leaves cranial cavity through the
internal acoustic meatus
Enters the facial canal within the
petrous part of temporal bone
Runs laterally above the vestibule
of internal ear
Reaches the medial wall of the
middle ear and bends sharply
backward above the promontory.
At the bend possesses the
geniculate ganglion
On reaching the posterior wall of
the middle ear cavity it bends
downward on the medial side of
the aditus to mastoid antrum and
then descends behind the pyramid
to exit from the stylomastoid
foramen
Branches of the Intrapetrous Part of the Facial Nerve
Greater petrosal nerve arises from the facial
nerve at the geniculate ganglion..The nerve
emerges on the superior surface of the petrous
part of the temporal bone and is eventually
joined by the deep petrosal nerve & forms the
nerve of the pterygoid canal, which ends in the
pterygopalatine ganglion.
Nerve to the stapedius arises from the facial
nerve as it descends in the facial canal behind
the pyramid. It supplies the muscle within the
pyramid.
Chorda tympani arises from the facial nerve
just above the stylomastoid foramen. It enters
the middle ear close to the posterior border of
the tympanic membrane. It then runs forward
over the tympanic membrane and crosses the
root of the handle of the malleus. The nerve
leaves the middle ear through the
petrotympanic fissure and enters the
infratemporal fossa, where it joins the lingual
nerve
Auditory Tube (Eustachian Tube)
The channel through which the
tympanic cavity communicates
with the nasopharynx.
Formed partly of bone
(posterior 1/3), partly of
cartilage and fibrous tissue
(anterior 2/3)
The mucous membrane of the
tube is continuous with that of
the nasopharynx, and the
tympanic cavity
The Eustachian tube functions
to equalize air pressure on both
sides of the eardrum.
Mastoid Antrum
The Mastoid Antrum lies behind the middle ear in the
petrous part of the temporal bone. It communicates with the
middle ear by the aditus
Relations:
 Anterior wall is related to the middle ear and contains
the aditus to the mastoid antrum
 Posterior wall separates the antrum from the sigmoid
venous sinus and the cerebellum
 Lateral wall is (1.5 cm) thick and forms the floor of the
suprameatal triangle
 Medial wall is related to the posterior semicircular
canal
 Superior wall is the thin plate of bone, the tegmen
tympani, which is related to the meninges of the middle
cranial fossa and the temporal lobe of the brain
 Inferior wall is perforated with holes, through which the
antrum communicates with the mastoid air cells
Mastoid Air Cells

The mastoid air cells are a series of communicating
cavities within the process that are continuous above
with the antrum and the middle ear.They are lined with
mucous membrane.
Inner Ear
The inner ear is made up of both
hearing (auditory) and balance
(vestibular) components &
functions to convert mechanical
energy into neural impulses.
Situated in the petrous part of
the temporal bone, medial to the
middle ear
Consists of a delicate
membranous inner ear, the
membranous labyrinth enclosed
and protected by a bony
chamber that is referred to as
the bony labyrinth
There are three main divisions of
the bony labyrinth.
 Vestibule :
 Lies medial to the oval window
 Contains the utricle and the
saccule, two organs of balance
 Leads to both the cochlea and the
semicircular canal
 Cochlea:
 A snail-shaped chamber anterior
to the vestibule
 Bulges into the middle ear as
promontory on its medial wall
 Communicates with the middle
ear via the round window.
 Converts sound waves into neural
impulses
Semicircular canals
cochlea
vestibule

Semicircular Canals:
 Three in number
 Project posteriorly from the
vestibule
 Consist of a superior,
posterior and lateral
(horizontal) canals
 These organs detect angular
acceleration
There are two compartments of
fluid in the inner ear
 The space within the bony
labyrinth surrounding the
membranous labyrinth
contains perilymph
 The space within the
membranous labyrinth
contains endolymph
The nerve fibers from the
labyrinth make up the
auditory nerve which
consists of a:
 Cochlear nerve and
 Vestibular nerve with
both afferent and efferent
fibers from the respective
sensory end organs.
The auditory nerve enters
the cranial cavity via the
internal auditory meatus
Clinical Notes
The otoscopic exam is
performed by gently pulling the
auricle upward and backward.
In children, the auricle should
be pulled downward and
backward. This process will
move the acoustic meatus in
line with the canal.
Too much cerumen can block
sound transmission.
This ear-throat connection
makes the ear susceptible to
infection (otitis media).
Infection of mastoid air cells