Outer ear

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Outer ear
A diagram of the anatomy of the human ear:   Brown is outer ear.   Red is middle ear.   Purple is inner ear.
The auricula. Lateral surface.
Details
Identifiers
Latin	auris externa
MeSH	D004431
NeuroLex ID	birnlex_1705
TA98	A15.3.01.001
TA2	6862
FMA	52781
Anatomical terminology [edit on Wikidata]

This article is one of a series documenting the anatomy of the
Human ear
Outer ear Auricle Ear canal
Middle ear Tympanic membrane Ossicles Malleus Incus Stapes
Inner ear Vestibules Utricle Saccule Cochlea Semicircular canals
v t e

The outer ear, external ear, or auris externa is the external part of the

Structure

Auricle

The visible part is called the

From the pinna, the

• The helicis major is a narrow vertical band situated upon the anterior margin of the helix. It arises below, from the spina helicis, and is inserted into the anterior border of the helix, just where it is about to curve backward.
• The helicis minor is an oblique fasciculus, covering the crus helicis.
• The tragicus is a short, flattened vertical band on the lateral surface of the tragus. Also known as the mini lobe.
• The antitragicus arises from the outer part of the antitragus, and is inserted into the cauda helicis and antihelix.
• The
  scapha
  .
• The
  concha
  to the convexity immediately above it.

The intrinsic muscles contribute to the topography of the auricle, while also function as a sphincter of the external auditory meatus. It has been suggested that during prenatal development in the womb, these muscles exert forces on the cartilage which in turn affects the shaping of the ear.^[3]

Extrinsic muscles

The extrinsic auricular muscles are the three

• anterior auricular muscle
• superior auricular muscle
• posterior auricular muscle

The superior muscle is the largest of the three, followed by the posterior and the anterior.

In some mammals these muscles can adjust the direction of the pinna. In humans these muscles possess very little action. The auricularis anterior draws the auricula forward and upward, the auricularis superior slightly raises it, and the auricularis posterior draws it backward. The superior auricular muscle also acts as a stabilizer of the occipitofrontalis muscle and as a weak brow lifter.^[4] The presence of auriculomotor activity in the posterior auricular muscle causes the muscle to contract and cause the pinna to be pulled backwards and flatten when exposed to sudden, surprising sounds.^[5]

Function

This section needs expansion. You can help by adding to it. (December 2013)

One consequence of the configuration of the outer ear is selectively to boost the sound pressure 30- to 100-fold for frequencies around 3 kHz. This amplification makes humans most sensitive to frequencies in this range—and also explains why they are particularly prone to acoustical injury and hearing loss near this frequency. Most human speech sounds are also distributed in the bandwidth around 3 kHz.^[6]

Clinical significance

Malformations of the external ear can be a consequence of

• A
  autosomal recessive fashion and may suffer from chronic infection in later life.^[7]
• Cosmetic defects, such as very large ears, small ears.[8]^[9]
• Malformation that may lead to functional impairment, such as atresia of the external auditory meatus^[10] or aplasia of the pinna,^[11]
• Genetic syndromes, which include:
  • autosomal recessive manner.^[12]
  • autosomal dominant manner.^[13]
  • sensorineural and conductive), inherited in an autosomal dominant manner.^[14][15]
  • autosomal dominant manner.^[16]

Usually, malformations are treated with surgery, although artificial prostheses are also sometimes used.[9]

• Preauricular fistulas are generally not treated unless chronically inflamed.^[9]
• Cosmetic defects without functional impairment are generally repaired after ages 6–7.^[17]

If malformations are accompanied by hearing loss amenable to correction, then the early use of hearing aids may prevent complete hearing loss.^[17]

Additional images

• 
  External and middle ear, opened from the front. Right side.

References

This article incorporates text in the public domain from page 1033 of the 20th edition of Gray's Anatomy (1918)