|Eardrum or Tympanic membrane|
|Anatomy of the human ear.|
|Right tympanic membrane as seen through a speculum.|
|Gray's||subject #230 1039|
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.
There are two general regions of the tympanic membrane: the pars flaccida (upper region, see picture on right) 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 thickened to form a fibrocartilaginous ring called the annulus tympanicus. The central part of the pars tensa is tented inwards at the level of the tip of malleus and is called the umbo. A cone of light can be seen radiating from the tip of the malleus to the periphery in the antero-inferior quadrant. The pars flaccida is situated above the lateral process of the malleus between the notch of Rivinus and the anterior and posterior malleal folds. It appears slightly pinkish.
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.
Unintentional rupture of the ear drum has been described in blast injuries during conflict, but also during air travel, usually when the congestion of an upper respiratory infection has prevented equalization of pressure in the middle ear. It is also described 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 this, 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.
- 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/
- Marchioni D, Molteni G, Presutti L (2011 February ). "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.
- Ritenour AE, Wickley A, Ritenour JS, Kriete BR, Blackbourne LH, Holcomb JB, Wade CE (2008 Feb). "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.
- Mirza S, Richardson H (2005 May). "Otic barotrauma from air travel". J Laryngol Otol. 119(5) (5): 366–70. doi:10.1258/0022215053945723. PMID 15949100.
- Green SM, Rothrock SG, Green EA= (1993 Oct). "Tympanometric evaluation of middle ear barotrauma during recreational scuba diving". Int J Sports Med. 14(7) (7): 411–5. doi:10.1055/s-2007-1021201. PMID 8244609.
- Fields JD, McKeag DB, Turner JL (2008 Feb). "Traumatic tympanic membrane rupture in a mixed martial arts competition". Current Sports Med Rep 7(1) (1): 10–11. doi:10.1097/01.CSMR.0000308672.53182.3b. PMID 18296937 .
- Kristensen S (1992 Dec). "Spontaneous healing of traumatic tympanic membrane perforations in man: a century of experience". J Laryngol Otol. 106(12) (12): 1037–50. PMID 1487657.
- Lindeman P, Edström S, Granström G, Jacobsson S, von Sydow C, Westin T, Aberg B (1987 Dec). "Acute traumatic tympanic membrane perforations. Cover or observe?". Arch Otolaryngol Head Neck Surg. 113(12) (12): 1285–7. PMID 3675893.
- Garth RJ (1995 Jul). "Blast injury of the ear: an overview and guide to management". Injury. 26(6): 363–6. PMID 363-6.
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