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
Identifiers
Latin membrana tympanica
MeSH A09.246.272.702
Dorlands
/Elsevier		 Tympanic membrane
TA A15.3.01.052
FMA 9595

Anatomical terminology

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.[1]

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 in the 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.[2]

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.

Innervation

Sensory innervation of the external surface of the tympanic membrane is mainly by the auricotemporal nerve, a branch of the mandibular nerve [V3]. It also has contributions from the auricular branch of the vagus nerve [X], the facial nerve [VII] and a possible contribution from the glossopharyngeal nerve [IX]. Sensory innervation of the inner surface of the tympanic membrane is by the glossopharyngeal nerve [IX].[3]

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.[4]

Clinical significance

Rupture

Unintentional rupture of the ear drum has been described in blast injuries during conflict[5] and air travel, usually when the congestion of an upper respiratory infection has prevented equalization of pressure in the middle ear.[6] It happens in sport and recreation, such as swimming, diving with a poor entry into the water, scuba diving,[7] and martial arts.[8] In the published literature, 80% to 95% have recovered completely without intervention in two to four weeks.[9][10][11]

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.[11]

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.[12]

See also

Wikimedia Commons has media related to Eardrum.

Additional images

References

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

  1. ↑ Purves D, Augustine GJ, Fitzpatrick D, et al., editors. Neuroscience. 2nd edition. Sunderland (MA): Sinauer Associates; 2001. The Middle Ear. Available from http://www.ncbi.nlm.nih.gov/books/NBK11076/
  2. ↑ Marchioni D, Molteni G, Presutti L (February 2011). "Endoscopic Anatomy of the Middle Ear". Indian J Otolaryngol Head Neck Surg 63 (2): 101–13. doi:10.1007/s12070-011-0159-0. PMC 3102170. PMID 22468244.
  3. ↑ Drake, Richard L., A. Wade Vogl, and Adam Mithcell. Gray's Anatomy For Students. 3rd ed. Philadelphia: Churchill Livingstone, 2015. Print. pg. 969
  4. ↑ Gray's Anatomy (1918)
  5. ↑ Ritenour AE, Wickley A, Retinue JS, Kriete BR, Blackbourne LH, Holcomb JB, Wade CE (February 2008). "Tympanic membrane perforation and hearing loss from blast overpressure in Operation Enduring Freedom and Operation Iraqi Freedom wounded". J Trauma 64 (2 Suppl): S174–8. doi:10.1097/ta.0b013e318160773e.
  6. ↑ Mirza S, Richardson H (May 2005). "Otic barotrauma from air travel". J Laryngol Otol 119 (5): 366–70. doi:10.1258/0022215053945723. PMID 15949100.
  7. ↑ Green SM, Rothrock SG, Green EA= (October 1993). "Tympanometric evaluation of middle ear barotrauma during recreational scuba diving". Int J Sports Med 14 (7): 411–5. doi:10.1055/s-2007-1021201. PMID 8244609.
  8. ↑ Fields JD, McKeag DB, Turner JL (February 2008). "Traumatic tympanic membrane rupture in a mixed martial arts competition". Current Sports Med Rep 7 (1): 10–11. doi:10.1097/01.CSMR.0000308672.53182.3b. PMID 18296937.
  9. ↑ Kristensen S (December 1992). "Spontaneous healing of traumatic tympanic membrane perforations in man: a century of experience". J Laryngol Otol 106 (12): 1037–50. doi:10.1017/s0022215100121723. PMID 1487657.
  10. ↑ Lindeman P, Edström S, Granström G, Jacobsson S, von Sydow C, Westin T, Aberg B (December 1987). "Acute traumatic tympanic membrane perforations. Cover or observe?". Arch Otolaryngol Head Neck Surg 113 (12): 1285–7. doi:10.1001/archotol.1987.01860120031002. PMID 3675893.
  11. 1 2 Garth RJ (July 1995). "Blast injury of the ear: an overview and guide to management". Injury 26 (6): 363–6. doi:10.1016/0020-1383(95)00042-8.
  12. ↑ Langenheim, Johnny (18 September 2010). "The last of the sea nomads". The Guardian. Retrieved 15 February 2016.

External links

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