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External and middle ear: applied anatomy

  • Applied anatomy

The outer ear funnels sound to the eardrum; three tiny bones in the air-filled middle ear pass it on to the inner ear.

Updated

See it in 3D: Auricle · Eardrum · Malleus · Incus · Stapes

What it is

The external ear (auricle and ear canal) collects sound and ends at the tympanic membrane. Behind it, the middle ear is an air-filled cavity in the temporal bone that holds the malleus, incus and stapes, is ventilated by the Eustachian tube from the nasopharynx and opens back into the mastoid air cells. Knowing these landmarks lets you read the eardrum on otoscopy, explain why children get otitis media, and recognise when an ear infection has spread to bone.

Applied anatomy

  • Auricle and external auditory canal: direct sound into the temporal bone to the tympanic membrane.
  • Tympanic membrane: pars tensa (skin, fibrous layer, mucosa, thick annulus) and pars flaccida above the lateral process of the malleus.
  • Ossicular chain, in order: malleus (handle attached to the drum), incus, stapes (footplate in the oval window).
  • Eustachian tube: links the middle ear to the nasopharynx; in adults about a third bony and two thirds cartilaginous; opened by the tensor veli palatini when swallowing or yawning.
  • Mastoid: honeycomb of air cells behind the ear, continuous with the middle ear.
  • Facial nerve: crosses the middle ear (tympanic segment) and descends in the mastoid, so ear disease and ear surgery can injure it.

Clinical physiology

  • The drum and ossicles amplify vibration and deliver it to the oval window; the Eustachian tube equalises pressure across the drum.
  • Poor tube function causes negative middle ear pressure, retraction of the drum and fluid (otitis media with effusion).

Clinical correlation

  • Otitis externa: canal skin infection, usually bacterial; pain when the outer ear is pulled or pressed; discharge and itching.
  • Malignant otitis externa: spread from the canal to the skull base bone, usually Pseudomonas, in diabetic, elderly or immunosuppressed patients; may cause facial weakness and dysphagia.
  • Acute otitis media: a cold blocks the Eustachian tube; enlarged adenoids near its opening add to the risk in children.
  • Cholesteatoma: a retraction pocket fills with keratin and erodes ossicles, the facial nerve and the inner ear; suspect it in chronic foul discharge with hearing loss.
  • Mastoiditis: complication of otitis media, mostly in children; can lead to meningitis, abscess, facial palsy and hearing loss.
  • Referred earache: the ear shares nerves with teeth, jaw joint, tonsils and throat; a normal ear with otalgia needs those areas examined.

Next step / Initial management

  • Examine with otoscopy: canal (oedema, debris), drum (colour, position, perforation, fluid level), and palpate the mastoid and the tragus.
  • Otitis externa: clean the canal and use topical antibiotic drops (with a wick if the canal is swollen); analgesia; keep the ear dry.
  • Acute otitis media in a child: analgesia, and observation or an aminopenicillin according to age and severity; confirm effusion before treating.
  • Refer the same day (emergency) for suspected mastoiditis, malignant otitis externa, or otitis with facial palsy, vertigo or neurological signs.
  • Refer routinely to ENT for chronic discharge, a retraction pocket or suspected cholesteatoma, a persistent perforation, or effusion with hearing loss lasting months.

Test yourself

Think of the answer, then tap the question to see it.

A 4-year-old has a red, bulging ear drum after a cold. Which anatomical feature explains why children get this more often than adults?

Their Eustachian tube is shorter and more horizontal, so the middle ear drains poorly; adenoids near its opening and an immature immune system add to the risk.

A 72-year-old diabetic has weeks of deep ear pain, discharge and new facial weakness despite drops. What must be ruled out?

Malignant (necrotising) otitis externa: Pseudomonas spreading to the skull base bone. It needs urgent imaging, long-course antibiotics and same-day ENT referral.

Where is the normal cone of light on the right tympanic membrane?

Anteroinferiorly, running from the tip of the malleus handle (umbo) towards the front lower edge of the drum.

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The structures of Durgical's 3D anatomy where it is found.

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Educational content; it does not replace a medical assessment and is not a clinical instruction. For a real case, follow current guidelines and specialist advice.

Sources: Primary ear and hearing care: training manual (World Health Organization, 2023); Ear Infections in Children (National Institute on Deafness and Other Communication Disorders (NIDCD), NIH, 2022); Swimmer's ear (MedlinePlus, US National Library of Medicine, 2024); Malignant otitis externa (MedlinePlus, US National Library of Medicine, 2026); Mastoiditis (MedlinePlus, US National Library of Medicine, 2026); Cholesteatoma (MedlinePlus, US National Library of Medicine, 2026).

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