Revision 16 for 'External ear'

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External ear

The external ear comprises the auricle (or pinna), the external auditory meatus, and the tympanum (eardrum). The pinna concentrates and amplifies sound waves and funnels them through the outer acoustic pore into the external auditory meatus, which carries them to the tympanic membrane.

Gross anatomy

Auricle (pinna)

The auricle is an irregularly-shaped plate of elastic cartilage and dense connective tissue covered by skin, which contains short hairs (tragi), sebaceous glands, and ceruminous glands.

Structure of the auricle

The auricle has a complex shape that is composed of several ridges, notches, and grooves:

  • helix: posterior free margin of the auricle
  • anthelix: a ridge parallel to the helix; possesses a pair of limbs, the crura anthelicis
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External auditory meatus

The external auditory meatus is a short canal leading from the auricle to the tympanic membrane. It is lined by skin containing hair follicles (tragi), sebaceous glands, and ceruminous glands.

Tympanum

The tympanic membrane consists of two layers of collagen fibers:

  • an outer layer with a radial fiber arrangement
  • an inner layer with a circular fiber arrangement

It has an outer cover of extremely thin skin and an inner layer of cuboidal epithelium facing the tympanic cavity.

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