M01.02.028 The External Ear

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Learning Objective: By the end of this session, the learner should be able to describe the anatomy of the external ear, including the auricle, external acoustic meatus, and tympanic membrane, and explain their neurovascular supply and clinical relevance, such as auricular hematoma and tympanic membrane perforation.

The ear is divided into three parts: the external, middle, and inner ear. The external ear includes the auricle (pinna) and the external acoustic meatus, ending at the tympanic membrane. Its primary function is to capture and direct sound waves toward the middle and inner ear.

Auricle (Pinna)

The auricle is a paired, mostly cartilaginous structure on each side of the head. It helps funnel sound into the ear canal.

Helix: Outer curved rim.
Antihelix: Inner curved ridge dividing into two crura.
Concha: Deep hollow leading into the external acoustic meatus.
Tragus and antitragus: Cartilaginous elevations flanking the entrance to the ear canal.
Lobule: The only non-cartilaginous part, composed of adipose tissue.

Clinical Correlation: Auricular Haematoma

An auricular haematoma is a collection of blood between the cartilage and perichondrium due to trauma (e.g., wrestling or rugby injuries). If untreated, it may lead to avascular necrosis and a “cauliflower ear” deformity.

External Acoustic Meatus

The external acoustic meatus is an S-shaped canal extending from the concha to the tympanic membrane.

Outer 1/3: Cartilaginous
Inner 2/3: Bony (temporal bone)

Curvature pathway:

Superoanteriorly
Superoposteriorly
Inferoanteriorly (ending at the tympanic membrane)

Tympanic Membrane (Eardrum)

The tympanic membrane marks the boundary between the external and middle ear. It is a thin connective tissue layer covered externally by skin and internally by mucosa.

Umbo: Point of attachment of the malleus handle.
Lateral process of the malleus: Visible projection superiorly.
Anterior and posterior malleolar folds radiate from it.

Clinical correlation:
Perforation may occur due to infection (otitis media) or trauma.
Small perforations often heal spontaneously, while larger ones may require surgical repair.

Vasculature

Supplied mainly by branches of the external carotid artery:

Posterior auricular artery
Superficial temporal artery
Occipital artery
Deep auricular branch of the maxillary artery (deep ear canal and tympanic membrane)

Venous drainage: Follows corresponding arteries.

Innervation

Greater auricular nerve (C2, C3)
Lesser occipital nerve (C2)
Auriculotemporal nerve (branch of mandibular nerve, CN V3)
Facial (CN VII) and vagus (CN X) nerves – supply deeper regions.
Stimulation of the auricular branch of the vagus nerve can cause an involuntary cough reflex during ear cleaning.