Branchial membrane

For other uses, see Eardrum (disambiguation).
Eardrum or Tympanic membrane
Anatomy of the human ear.
Right tympanic membrane as seen through a speculum.
Latin membrana tympanica
Gray's subject #230 1039
MeSH Tympanic+Membrane
Dorlands/Elsevier Tympanic membrane

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]

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.[2]

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

Parts

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.

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.

Intentional rupture

The Bajau people of the Pacific intentionally rupture their eardrums at an early age in order to facilitate diving and hunting at sea. Many older Bajau therefore have difficulties hearing.[3]

Unintentional rupture

Unintentional rupture of the ear drum has been described in blast injuries during conflict,[4] but also during air travel, usually when the congestion of an upper respiratory infection has prevented equalization of pressure in the middle ear.[5] It is also described in sport and recreation, such as swimming, diving with a poor entry into the water, scuba diving[6] and martial arts.[7] In the published literature, 80% to 95% have recovered completely without intervention in two to four weeks.[8][9] [10] 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.[10]

See also

Gallery

References

External links

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