Eardrum

For other uses, see Eardrum (disambiguation).

Not to be confused with the secondary tympanic membrane of the round window

Eardrum or Tympanic membrane
Right tympanic membrane as seen through a speculum.
Details
Latin	membrana tympanica
Identifiers
MeSH	A09.246.272.702
Dorlands /Elsevier	Tympanic membrane
TA
TH	{{#property:P1694}}
TE	{{#property:P1693}}
FMA	{{#property:P1402}}
Anatomical terminology [[[d:|edit on Wikidata]]]

In human anatomy, the eardrum, or tympanic membrane, is a thin, cone-shaped membrane that separates the external ear from the middle ear in humans and other tetrapods. Its function is to transmit sound from the air to the ossicles inside the middle ear, and then to the oval window in the fluid-filled cochlea. Hence, it ultimately converts and amplifies vibration in air to vibration in fluid. The malleus bone bridges the gap between the eardrum and the other ossicles.

Rupture or perforation of the eardrum can lead to conductive hearing loss. Collapse or retraction of the eardrum can cause conductive hearing loss or cholesteatoma.

Structure

There are two general regions of the tympanic membrane: the pars flaccida upper region and the pars tensa. The pars flaccida consists of two layers, is relatively fragile, and is associated with eustachian tube dysfunction and cholesteatomas. The larger pars tensa region consists of three layers: skin, fibrous tissue, and mucosa. It is comparatively robust and is the region most commonly associated with perforations.

The pars tensa forms most of the tympanic membrane. Its periphery is thick and forms a fibrocartilaginous ring called the anulus tympanicus. The central part of the pars tensa is tented inward at the level of the tip of malleus and is called the umbo. A cone of light radiates from the tip of the malleus to the periphery in the antero-inferior quadrant. The pars flaccida is above the lateral process of the malleus between the notch of Rivinus and the anterior and posterior malleal folds. It appears slightly pinkish.

Relations

The tympanic membrane is superiorly related to middle cranial fossa, posteriorly to the ear ossicles and the facial nerve, inferiorly to the parotid gland and anteriorly to the temporomandibular joint.

Umbo

The umbo is the most depressed part of the tympanic membrane. The manubrium of the malleus is firmly attached to the medial surface of the membrane as far as its center, which it draws toward the tympanic cavity; the lateral surface of the membrane is thus concave, and the most depressed part of this concavity is named the umbo.

Clinical significance

Rupture

Unintentional rupture of the ear drum has been described in blast injuries during conflict and air travel, usually when the congestion of an upper respiratory infection has prevented equalization of pressure in the middle ear. It happens in sport and recreation, such as swimming, diving with a poor entry into the water, scuba diving, and martial arts. In the published literature, 80% to 95% have recovered completely without intervention in two to four weeks.

These injuries, even in a recreational or athletic setting, are blast injuries. Many will experience some short-lived hearing loss and ringing in the ear (tinnitus) but can be reassured that it, in all likelihood, will pass. A very few will experience temporary disequilibrium (vertigo). There may be some bleeding from the ear canal if the eardrum has been ruptured. Naturally, the foregoing reassurances become more guarded as the force of injury increases, as in military or combat situations.

Society and culture

The Bajau people of the Pacific intentionally rupture their eardrums at an early age to facilitate diving and hunting at sea. Many older Bajau therefore have difficulties hearing.

See also

• Middle ear
• Valsalva maneuver to equalize pressure across the eardrum

Additional images

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  External and middle ear, opened from the front (right side)

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  Horizontal section through left ear; upper half of section

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  The right membrana tympani with the hammer and the chorda tympani, viewed from within, from behind, and from above

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  Auditory tube, laid open by a cut in its long axis

• Gray919.png

  Chain of ossicles and their ligaments, seen from the front in a vertical, transverse section of the tympanum

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  Right tympanic membrane as seen through a speculum

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  This is a normal left tympanic membrane [eardrum].

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  Tympanic membrane viewed by otoscope

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  The oval perforation in this left tympanic membrane was the result of a slap on the ear

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  A subtotal perforation of the right tympanic membrane resulting from a previous severe otitis media

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  A normal human right tympanic membrane (eardrum)

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  Frog on leaf showing eardrum

References

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

External links

• Diagram at Georgia State University
• drtbalu's otolaryngology online