THE EAR

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THE EAR
Dr. Ahmed Fathalla Ibrahim
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THE EAR

• Is an organ of hearing balance
• Consists of three parts
• External Ear
• Middle Ear
• Internal Ear

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THE EXTERNAL EAR

• AURICLE
• EXTERNAL AUDITORY MEATUS

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AURICLE

• Shape consists of a thin plate of elastic
  cartilage
• Function collects air vibrations
• Motor supply facial nerve

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EXTERNAL AUDITORY MEATUS

• Shape a curved tube formed of elastic cartilage
  (outer 1/3) tympanic plate of temporal bone
  (inner 2/3)
• Function conducts sound waves from auricle to
  tympanic membrane

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THE MIDDLE EAR (TYMPANIC CAVITY)

• Definition air-containing cavity in petrous part
  of tympanic bone, lined with mucus membrane
• Function transmits vibration of tympanic
  membrane to perilymph of internal ear
• Communications
• Anteriorly with nasopharynx (through auditory
  tube)
• Posteriorly with mastoid antrum
• Nerve supply tympanic branch of glossopharyngeal
  nerve

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THE MIDDLE EAR

• Roof tegmen typani (thin plate from petrous
  temporal bone), separates middle ear from
  temporal lobe of brain
• Floor thin plate of bone, separates middle ear
  from superior bulb of internal jugular vein

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THE MIDDLE EAR

• Anterior wall
• Superiorly has 2 openings (for auditory tube
  for canal of tensor tympani)
• Inferiorly thin plate of bone separating middle
  ear from internal carotid artery

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THE MIDDLE EAR

• Posterior wall
• Superiorly has an opening (aditus to mastoid
  antrum)
• Inferiorly a conical projection (pyramid) for
  emergence of stapedius

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THE MIDDLE EAR

• Lateral wall tympanic membrane
• Medial wall
• Promontory rounded projection formed by cochlea
• Fenestra vestibuli oval opening, above behind
  promontory, closed by base of stapes
• Fenestra cochleae round opening below
  promontory, closed by secondary tympanic membrane
• Prominence for facial nerve canal runs backward
  above promontory fenestra vestibuli then curves
  downward behind pyramid

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THE TYMPANIC MEMBRANE

• Shape a thin fibrous membrane between external
  middle ear, has a small depression (umbo)
  produced by handle of malleus, divided into pars
  flaccida pars tensa
• Nerve supply
• Outer surface auricular branch of vagus
• Inner surface tympanic branch of glossopharyngeal

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AUDITORY OSSICLES

• MALLEUS
• Head articulates with body of incus
• Neck
• Handle firmly attached to medial surface of
  tympanic membrane, receives insertion of tensor
  tympani
• Anterior process
• Lateral process attached to anterior posterior
  malleolar folds of tympanic membrane

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AUDITORY OSSICLES

• INCUS
• Body articulates with head of malleus
• Long process articulates with head of stapes
• Short process attached to tympanic cavity

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AUDITORY OSSICLES

• STAPES
• Head articulates with long process of incus
• NecK receives insertion of stapedius
• Base attached to fenestra vestibuli

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MUSCLES OF OSSICLES

• TENSOR TYMPANI
• Origin auditory tube
• Insertion handle of malleus
• Nerve supply mandibular of trigeminal
• Action damps down vibration of tympanic membrane
• STAPEDIUS
• Origin pyramid
• Insertion neck of stapes
• Nerve supply facial
• Action damps down vibration of stapes

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FACIAL NERVE

• Course runs in facial canal then emerges through
  stylomastoid foramen
• Branches
• Nerve to stapedius
• Chorda tympani carries taste fibers from
  anterior 2/3 of tongue preganglionic
  parasympathetic fibers to submandibular
  sublingual salivary glands
• Greater petrosal nerve carries taste fibers from
  soft palate preganglionic parasympathetic
  fibers to lacrimal, nasal palatine glands

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THE INTERNAL EAR

• Lies in petrous part of temporal bone
• Consists of
• Bony labyrinth
• Membranous labyrinth

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BONY LABYRINTH

• Consists of
• Vestibule
• 3 semicircular canals
• Cochlea
• They are cavities inside bone, filled with
  perilymph in which membranous labyrinth is
  suspended

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MEMBRANOUS LABYRINTH

• Lodged within bony labyrinth
• Filled with endolymph surrounded by perilymph
• Consists of
• Utricle saccule in vestibule
• 3 semicircular ducts in semicircular canals
• Cochlear duct in cochlea

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VESTIBULOCOCHLEAR NERVE

• Divides into
• Vestibular nerve supplies utricle, saccule
  semicircular ducts
• Cochlear nerve supplies cochlear duct

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