EAR

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EAR
DR. JAMILA EL MEDANY
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VESTIBULOCOCCHLEAR ORGAN

• It is divided into
• External ear.
• Middle ear (Tympanic cavity).
• Internal ear (Labyrinth).

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EXTERNAL EAR

• Auricle
• Attached to the lateral aspect of the head.
• External Auditory (Acoustic) meatus
• A canal leading inwards.
• It is (S) shaped tube .
• (2.5 cm) in adults.
• Its lateral 1/3 is Cartilaginous.
• It is lined with Skin.
• It contains hairs, sebaceous and many Ceruminous
  glands

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EXTERNAL AUDITORY MEATUS

• Its medial 2/3 is Bony.
• Formed mainly by the Tympanic Plate.
• It is lined by thin skin.
• Nerve Supply Auriculotemporal nerve.
• Auricular branch of the vagus.

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OTOSCOPY

• The meatus has to be straight.
• It is pulled
• In Children
• Straight backward or downward and backward.
• In Adults
• Upward and backward.

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TYMPANIC MEMBRANE

• It is an oval, thin semitransparent membrane (1
  cm) in diameter.
• It forms a Partition between the external meatus
  and the tympanic cavity.

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ON OTOSCOPY

• A shallow cone like central depression , its peak
  is the Umbo.
• Cone of light radiates antero inferior from the
  umbo.
• Pars Flaccida
• The thin superior part of the membrane.
• Pars Tensa
• The rest of the membrane.
• It is thick and taut.

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NERVE SUPPLY

• The tympanic membrane is extremely sensitive to
  pain.
• Outer surface (mainly)
• Auriculotemporal nerve
• Auricular branch of the vagus.
• Internal surface Glossopharyngeal nerve.

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MIDDLE EAR

• It is an air- filled mucous membrane lined space
  in the temporal bone.
• It is between
• Laterally
• The Tympanic membrane.
• Medially
• The lateral wall of the inner ear.

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PARTS

• (1) Tympanic Cavity
• A space directly internal to the tympanic
  membrane.
• (2) Epitympanic Recess
• A space superior to the tympanic cavity.

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CONNECTIONS

• (1) Anterior
• Nasopharynx
• (2) Postero superior
• Mastoid air cells.

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ROOF

• Tegmental Wall
• A thin plate of bone (Tegmen Tympani) on the
  anterior surface of the petrous part of temporal
  bone.
• It separates the cavity from
• Middle Cranial Fossa.

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FLOOR

• Jugular wall
• It is a thin plate of bone.
• It separates the cavity from the Superior Bulb of
  IJV.
• It may be deficient or replaced by fibrous
  tissue.

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LATERAL WALL

• Membranous
• Almost totally it is the Tympanic Membrane.
• Superiorly
• Epitympanic Recess.

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MEDIAL WALL

• Labyrinthine
• 1. Promontory
• A central bulge .
• Produced by the basal coil of the Cochlea
• 2. Tympanic Plexus.
• On the mucous membrane of the promontory.
• 3. Fenestra Vestibuli
• (Oval Window)
• It is above and behind the Promontry.
• 4. Fenestra Cochlea (Round window).
• The windows lead to Perilymph of internal ear.

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MEDIAL WALL

• 5. Prominence of facial canal
• posterior and superior to the oval window.
• Produced by the Facial nerve in its canal.
• 6. Prominence of lateral semicircular canal.

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OTOSCLEROSIS

• A pathological process affecting the mucosa of
  the Oval window and the mastoid process.
• They are transformed into bone.
• It is complicated by Deafness.

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ANTERIOR WALL

• Carotid
• Lower
• A thin plate of bone.
• It separates the tympanic cavity from the Carotid
  Canal.
• Upper Two openings
• Upper smaller for the Tensor Tympani.
• Lower larger for the Auditory Tube.

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POSTERIOR WALL

• Mastoid area
• A. Aditus
• A large irregular opening posterior to the
  epitympanic recess.
• B. Mastoid antrum
• A cavity continuous with air filled spaces within
  the mastoid process.
• C. Pyramid
• The tendon of Stapedius muscle emerges from its
  apex.

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MASTOID ANTRUM

• Roof Tegmen Tympani.
• Floor Many openings
• To communicate with the mastoid air cells.
• Anterior
• Middle ear Aditus.
• Posterior
• Sigmoid Sinus Cerebellum.
• Lateral
• Floor of Suprameatal Triangle.
• Medial
• Posterior Semicircular Canal.

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CONTENTS OF TYMPANIC CAVITY

• 1. Auditory Ossicles.
• 2. Muscles.
• 3. Nerves.

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AUDITORY OSSICLES

• They extend from the tympanic membrane to the
  oval window.
• They are present at Birth.
• Not covered by Periosteum.
• Malleus
• The largest and attached to the tympanic
  membrane.
• Stapes
• Occupies the oval window .
• Incus
• Between the two bones.
• Their decreased mobility in old age is
  responsible for degrees of Deafness.

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TENSOR TYMPANI

• It lies in a bony canal above the
  Pharyngotympanic tube.
• Insertion
• Handle of the malleus.
• Action
• Pulles the handle medially.
• Tenses the tympanic membrane.
• Reduces the amplitude of its oscillations.
• Nerve supply Mandibular

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STAPEDIUS

• The smallest voluntary muscle of the body.
• Origin
• From inside the pyramidal eminence.
• Insertion
• Neck of the stapes.
• Action
• Pulls the stapes posteriorly.
• Reduces the oscillatory range and prevents its
  excessive movements.
• Nerve supply Facial nerve.

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TYMPANIC NERVVE

• A branch of Glossopharyngeal nerve.
• Passes through the floor of the middle ear and
  onto the Promontry.
• Gives
• Tympanic Plexus
• It associates the Caroticotympanic Plexus to
  supply mucous membrane of middle ear.
• Lesser Petrosal nerve
• To Otic Ganglion.

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FASCIAL NERVE

• Enters
• 1.Internal acoustic meatus in close company with
  the 8th nerve.
• 2. Facial Canal.
• It continues laterally between the inner and
  middle ears.
• It expands to form the Geniculate Ganglion.

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FASCIAL NERVE

• At the posterior wall
• Curves downward in a vertical direction.
• Lies
• Medial to the Aditus.
• Behind the Pyramid.
• Exits
• Through the Stylomastoid Foramen.

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BRANCHES

• 1. Greater Petrosal nerve.
• It is the first branch from the Geniculate
• Ganglion.
• It carries preganglionic parasympathetic to the
  Pterygopalatine Ganglion.
• It supplies
• Lacrimal , Nasal and Palatine glands.

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BRANCHES

• 2. Nerve to Stapedius.
• 3. Chorda Tympani
• It arises just before the facial nerve exits.
• It ascends to enter the middle ear through its
  posterior wall.

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AUDITORY TUBE

• Connects the Tympanic Cavity to the Nasopharynx.
• Its Postero lateral 1/3 is bony.
• The remainder is Cartilaginous.
• Its walls are normally in apposition.
• The tube is actively opened by swallowing and
  yawing

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AUDITORY TUBE

• Function
• Equalizes pressure in the middle ear with the
  atmospheric pressure.
• It is a pathway of infection from the throat to
  the tympanic cavity and mastoid air cells.
• Nerve supply tympanic plexus.

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BONY LABYRINTH

• A series of bony cavities in the Petrous part of
  temporal bone.
• It is composed of
• Cochlea.
• Vestibule.
• Semicircular Canals.
• They contain Perilymph.

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BONY LABYRINTH

• Cochlea
• It is shell shaped .
• Its first turn produces the Promontory.
• Vestibule
• It is in a central position.
• It has the Oval and Round Windows in its lateral
  wall.
• Semicircular canals
• Posterior, superior and Lateral.
• They communicate with the Vestibule.

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MEMBRANOUS LABYRINTH

• It consists of
• Four Ducts
• Cochlear
• Three Semicircular
• Two Sacs
• Utricle.
• Sacuule.
• It is filled with Endolymph.
• It is separated from the periosteum of the bony
  labyrinth by Perilymph.

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COCHLEAR DUCT

• The cochlea is divided into two canals containing
  Perilymph by the centrally located cochlear duct.
• The duct has
• Roof Vestibular membrane.
• Floor Basilar membrane.
• The Spiral Organ (organ of hearing) rests on the
  basilar membrane.

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ORGANS OF BALANCE

• Utricle.
• Sacule
• Three Semicircular Ducts.
• The Utricosaccular Duct establishes
• continuity between all components of the
  membranous labyrinth.

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ORGANS OF BALANCE

• The Endolymphatic Duct branches from it.
• It emerges onto the posterior surface of the
  petrous part of the temporal bone.
• It expands to form an Extradural Pouch
  Endolymphatic Sac.

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VESTIBULOCOCHLEAR NERVE

• Divides into
• A. Vestibular nerve
• It enlarges to form the Vestibular Ganglion.
• It supplies
• Three semicircular ducts.
• Utricle Saccule.
• B. Cochlear nerve
• It enters the base of the cochlea.
• It innervates the receptors in the Spiral Organ.