Sense organs · Head and neck

Ear canal !

The ear canal is the S-shaped tube, about 2.5 cm long, from the outer ear to the eardrum; it carries sound inward and makes earwax.

Official name: External acoustic meatus

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What it is

The 2.5 cm S-shaped canal from the outer ear to the eardrum.

What it does

Carries sound to the eardrum; it makes wax and can get infected (swimmer's ear).

Key facts

Where

From the concha to the tympanic membrane (~2.5 cm, S-shaped)

Blood supply

Posterior auricular, maxillary, superficial temporal arteries

Nerve

V3 (auriculotemporal), X (Arnold's nerve: cough when touched); great auricular (C2–C3) to the back; small VII twig to the posterior wall

Function

Conducts sound; makes wax

Relations

Medial

Tympanic membrane, set obliquely so the anteroinferior canal wall is longer and forms a recess where debris collects

In front

Head of the mandible at the temporomandibular joint: jaw movement is felt with a finger in the canal, and a blow to the chin can fracture the anterior bony wall

Behind

Mastoid air cells; in mastoiditis the posterosuperior canal wall may sag

Above

Thin bone separating it from the middle cranial fossa and the temporal lobe

Below

Parotid gland; small gaps in the floor of the cartilage (fissures of Santorini) let infection or tumour pass between canal and parotid

How to find it

With the auricle drawn up and back, the otoscope speculum is passed just into the cartilaginous part (the bony part is very sensitive) and the eardrum is seen at the end, facing slightly down and forward. Wax normally migrates outward on its own with the skin of the canal.

Examination

• Tragal pressure or auricle traction causing sharp pain: otitis externa
• Otoscopy: a swollen, narrowed canal with debris (otitis externa), fluffy white or black material (fungal infection), wax plug, foreign body or bony swellings
• Rinne and Weber tests: wax or a foreign body blocking the canal produces a conductive pattern (Rinne negative, Weber to the blocked side)

On imaging

Seen directly with the otoscope. High-resolution temporal bone CT shows its bony part: narrowing or absence (atresia), exostoses (broad, often both sides, in cold-water swimmers), a single stalked osteoma, and bone erosion. In necrotising (malignant) otitis externa, CT shows erosion of the canal floor and skull base, and MRI shows soft tissue spread better.

Clinical notes

• Otitis externa (swimmer's ear) follows moisture, scratching or cotton-bud trauma that breaks the skin and its waxy barrier; Pseudomonas aeruginosa and Staphylococcus aureus are the usual bacteria
• Foreign bodies are common in young children; insects and button batteries are urgent, the latter because they burn the canal skin quickly
• Exostoses (surfer's ear): smooth bony swellings of the deep canal after repeated cold-water exposure; large ones trap water and wax
• Necrotising otitis externa can involve the facial nerve at the stylomastoid foramen and lower cranial nerves at the skull base

Development

The canal comes from the first pharyngeal cleft; a solid meatal plug later hollows out, and failure produces congenital aural atresia, often with a malformed auricle.

Related conditions

• Otitis externa
• Foreign bodies of the ear and nose

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Educational information, not medical advice. For any symptom, see a health professional.

Its names

Official Latin (TA2)

meatus acusticus externus TA2 6867

Official Spanish (DeCS)

Conducto Auditivo Externo DeCS D004424

English (TA2)

External acoustic meatus

Related

• Eardrum
• Auricle

Sources: Terminologia Anatomica (TA2); DeCS; Ear, Hearing, and Facial Nerve Evaluation; Otitis Externa.

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Representative model, for educational purposes only.