ANATOMY OF THE EAR

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ANATOMY OF THE EAR

• The organ of hearing and equilibrium
• Divided into three parts
• External ear
• Middle ear
• Internal ear

• External ear
• Includes
• The Auricle and
• The External acoustic meatus

Middle ear
Internal ear
External acoustic meatus
auricle
External ear
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External Ear Auricle

• Collects sound waves and directs them into the
  external acoustic meatus
• Formed of a thin plate of cartilage covered by
  skin
• Has a lateral and medial surfaces
• The lateral surfaces presents some elevations and
  depressions

Superior inferior crura of antihelix
Triangular fossa
Helix
Antihelix
Crus of helix

• Parts of the auricle
• Helix the curved margin of the auricle
• Begins anteriorly at a ridge called the crus of
  helix
• Ends postero-inferiorly at the lobule of the ear
• Antihelix a cruved ridge in front of the post.
  part of helix
• Superiorly it divides into sup. inf. crura
• The crura are separated by a the triangular fossa
• Scaphoid fossa depression between helix and
  antihelix
• Tragus a projection below the crus of helix
• Antitragus a small tubercle on the lower part of
  antihelix
• Concha the central depression of the auricle

Concha
Tragus
Antitragus
Lobule
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• Muscles of the auricle
• Extrinsic muscles
• Auricularis anterior
• Supplied by temporal branches of facial n.
• Auricularis superior
• Auricularis posterior, supplied by post auricular
  n. (from facial)
• Intrinsic muscles slips of striated muscles
  fibers, supplied by
• temporal and posterior auricular branches of
  facial n.

Auricularis superior
Auricularis posterior

• Arterial supply of the auricle
• Auricular branches of superficial temporal a.
• Auricular branch of posterior auricular a.
• Auricular branch of occipital a.

Auricularis anterior

• Sensory nerve supply of the auricle
• Great auricular supplies lower 1/3 of lateral
  surface lower 2/3 of medial surface
• Auriculotemporal supplies upper 2/3 of lateral
  surface
• Lesser occipital supplies upper 1/3 of medial
  surface
• Auricular branch of vagus supplies skin of
  concha
• Facial nerve supplies skin of concha via a
  communication with the auricular branch of vagus

External acoustic meatus
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External acoustic meatus

• The passage between the concha and the outer
  surface of tympanic membrane
• Conducts sound waves from the auricle to the
  tympanic membrane
• Measures 4 cm from the tragus (2.5 cm from bottom
  of concha)
• The lateral 1/3 forms the cartilagenous part of
  the meatus
• The medial 2/3 form the bony part of the meatus
• The anterior wall and floor of the meatus are
  longer than the roof and post wall
• (because of the obliquity of the tympanic
  membrane)
• The meatus is S-shaped and has 2 constrictions
• At the junction between the cartilagenous and
  bony parts
• In the bony part (5mm from the tympanic membrane)
• called the isthmus

External acoustic meatus

• The skin of the meatus is thin and firmly
  attached to its walls
• The outer 1/3 contains hairs and seruminous
  glands (secrete wax)

Tympanic membrane
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Tympanic Membrane

• An oval semitransparent membrane
• Obliquely situated at the bottom of the external
  acoustic meatus
• The circumference of the membrane is thick and
  fitted
• into the tympanic sulcus of temporal bone
• The upper part of the sulcus is deficient forming
  a notch
• Two fibrous bands connect the sides of the notch
  to the lateral
• process of malleus(anterior posterior
  malleolar folds)
• Three parts of the membrane can be recognized
• Pars flaccida the triangular area between the
  malleolar folds
• Pars tensa the greater part of the membrane
• Cone of light at the antero-inferior part of the
  membrane

Lateral process of malleus
Handle of malleus
External acoustic meatus

• The handle of malleus is attched to the center of
  the inner surface of the membrane leading to
  projection of the membrane towards the middle ear
• The membrane is concave laterally and convex
  medially

Posterior malleolar fold
anterior view
Pars flaccida
Handle of malleus
Anterior malleolar fold

• Layers of the tympanic membrane
• Outer cuticular layer
• Middle fibrous layer
• Inner mucous layer

Lateral process of malleus
Cone of light
Lateral view
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• Arterial supply of the external acoustic meatus
• Auricular branches of superficial temporal
• Auricular branch of posterior auricular
• Deep auricular (branch of maxillary)
• Arterial supply of the tympanic membrane
• Outer surface
• Deep auricular (branch of maxillary)
• Inner surface
• Anterior tympanic (maxillary)
• Posterior tympanic (stylomastoid artery)
• Carotico-tympanic (internal carotid artery)

• Nerve supply of the external acoustic meatus
• Auriculotemporal n supplies anterior wall and
  roof
• Auricular branch of vagus supplies floor and
  posterior wall
• Nerve supply of the tympanic membrane
• Outer surface same nerves which supply the
  external meatus
• Inner surface tympanic branch of
  glossopharyngeal

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Summary of arterial nerve supply of external
ear

• Nerve supply of the external ear
• Auriculotemporal n
• -upper 2/3 of lateral wall of auricle
• -anterior wall and roof of meatus
• -outer surface of tympanic membrane
• Auricular branch of vagus
• -concha of auricle
• -floor and posterior wall of meatus
• -outer surface of tympanic membrane
• Great auricular n
• -lower 1/3 of lateral surface of auricle
• -lower 2/3 of medial surface of auricle
• Lesser occipital n
• -upper 1/3 of medial surface of auricle
• Inner surface of tympanic membrane is supplied by
• tympanic branch of glossopharyngeal

• Arterial supply of the external ear
• Auricular branches of superficial temporal a.
• -lateral surface of auricle
• -external acoustic meatus
• Auricular branch of posterior auricular a.
• -medial surface of auricle
• -external acoustic meatus
• Deep auricular (of maxillary)
• -outer surface of tympanic membrane
• Inner surface of tympanic membrane is supplied
  by
• -Anterior tympanic (maxillary)
• -Posterior tympanic (stylomastoid)
• -Carotico-tympanic (internal carotid)