Eardrum

From Free net encyclopedia

Template:Infobox Anatomy The tympanic membrane, colloquially known as the eardrum, is a thin membrane that separates the external ear from the middle ear. Its function is to transmit sound from the air to the ossicles inside the middle ear. 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.

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Development

The tympanic membrane forms from the joining of the expanding first pharyngeal pouch and groove. Around day 30 of gestation, the endoderm-lined first pharyngeal pouch expands to form the tympanic cavity, which subsequently envelops the inner ear ossicles. Simultaneously, the first pharyngeal groove, which is lined with ectoderm, expands to form the developing external auditory meatus. Separated by a thin layer of mesoderm, the tympanic cavity and external auditory meatus join to form the tympanic membrane. As a result, the tympanic membrane is one of very few adult structures that is derived from all three germ layers.

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Damage

Rupture or perforation (hole) of the eardrum can occur in infection, trauma (e.g. by trying to clean the ear with sharp instruments), explosion or loud noise. Flying with a severe cold can also cause perforation due to changes in air pressure,[1] and blocked eustachian tubes resulting from the cold.Template:Fact This is especially true on landing. This leads to conductive hearing loss.

The perforation may heal in a few weeks, or up to a few months.[2] Some perforations require intervention - this may use a paper patch to promote healing (simple procedure in the office of an ear, nose and throat specialist), or surgery (tympanoplasty).[3][4]

Hearing is usually recovered fully, but chronic infection over a long period may lead to permanent hearing loss.

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