Tympanic cavity

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Position of the tympanic cavity (marked with ph )

The tympanic cavity ( Cavum tympani ) is the space in the middle ear in which the ossicles are located. It starts right behind the eardrum and is ventilated through the Eustachi tube , which enables pressure equalization.

The tympanic cavity is about 12-15 mm long and 3-7 mm wide. Their internal volume is small and is only about 1 cm 3 . It consists of three sections:

  • Timpani dome (Epitympanon)
  • Middle of the timpani (mesotympanum)
  • Timpani (hypotympanum)

Topographic anatomy

Epitympanon (Atticus / Attikus / Attic space)

The epitympanon (other names are Attikus, Atticus and Attikraum) is the uppermost section of the tympanic cavity above the upper edge of the eardrum. Here the tympanic cavity is separated from the middle cranial fossa by a thin plate of bone, which is called the tegmen tympani. The epitympanone also contains the hammer head and the anvil body as well as the access to the mastoid (aditus ad antrum (mastoideum)) - see also section Pars mastoidea in the article temporal bone .

The epitympanone is supplied with vessels via the superior tympanic artery from the middle meningeal artery .

Mesotympanum

The mesotympanum represents the middle section of the tympanic cavity. Its anatomical relationship to the neighboring structures is described by idealizing its delimitation to four walls:

Drawing of a prepared right tympanic cavity - right-outer view of the
ossicles removed. On the right is the exit of the tube ( Eustachian tube in the picture ). The round and oval windows are shown dark in the center of the picture. At the bottom left the branch of the timpani string (in the picture Chorda tympani ) from the VII cranial nerve (in the picture Facial N. ). The thin-walled demarcation of the tympanic cavity downwards ( jugular fossa in the picture ) is clearly visible. The stapedius muscle, not shown here, arises from the Eminentia pyramidalis ( pyramite in the picture ) . Underneath, the Apertura tympanica canaliculi chordae tympani (exit opening of the timpani string - the part of the timpani string that is exposed in the timpani cavity is dissected out)
  • Anterior wall (Paries caroticus tympani): The internal carotid artery runs behind it . In the caudal part of the wall, the auditory tuba joins the tympanic cavity. The origin of the tympanic membrane tension muscle ( Musculus tensor tympani ) lies above the confluence of the tube (Ostium tympanicum tubae auditivae ).
  • Lateral wall (Paries membranaceus tympani): It is formed almost exclusively by the eardrum .
  • Posterior wall (Paries mastoideus tympani): It separates the tympanic cavity from the mastoid process ( mastoid process ). In the superior-posterior area there is a connection to the pneumatic spaces of the mastoid (aditus ad antrum). At the level of the oval window (Fenestra ovalis) one can make out a pyramidal protrusion, the Eminentia pyramidalis, from which the stapedius muscle starts.
  • Middle wall (Paries labyrinthicus tympani): It separates the snail ( cochlea ) from the tympanic cavity. The so-called promontory lies between the oval window and the round window. This small protrusion is caused by the lower spiral.

The vascular supply for the area of ​​the tube mouth is provided via the anterior tympanic artery from the maxillary artery and from the posterior tympanic artery from the stylomastoid artery for the posterior sections of the tympanic cavity.

Hypotympanum

The hypotympanum forms the lower part of the tympanic cavity. The lower wall (paries jugularis tympani) of the hypotympanum delimits the tympanic cavity from the internal jugular vein . The bone at this point is partially pneumatized and very thin.

The inferior tympanic artery from the ascending pharyngeal artery supplies the hypotympanum.

Tympani

The tympanic bladder ( bulla tympanica ) is an enlarged lower pocket of the tympanic cavity that protrudes downward from the floor of the middle ear. It occurs mostly in mammals living in desert areas and promotes hearing of deep tones. Due to the size of the air space, the vibrations of the eardrum condense it less and thus particularly low tones are less attenuated . Since low tones carry far, this adaptation by listening over a greater distance is beneficial for living in open areas.

Web links

Wiktionary: Tympanic Cave  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ^ Pschyrembel Clinical Dictionary . Founded by Willibald Pschyrembel. Edited by the publisher's dictionary editor under the direction of Helmut Hildebrandt. 258th edition. De Gruyter, Berlin 1987, ISBN 3-11-014824-2
  2. ^ HG Boenninghaus: Ear, Nose and Throat Medicine for Medical Students. Springer, Berlin / Heidelberg / New York 1986, ISBN 3-540-16683-1 , p. 16
  3. ↑ Gerald Fleischer: Studies on the skeleton of the auditory organ of mammals including humans . In: Mammalian Communications . No. 21 , 1973, ISSN  0036-2344 , pp. 131-239 . → Quoted in: Dietrich Starck: Part 5: Mammals . In: Dietrich Starck (ed.): Textbook of Special Zoology. Volume II: Vertebrates . Gustav Fischer, Jena / Stuttgart / New York 1995, ISBN 3-334-60453-5 (1241 pages; p. 48).
This text is based in whole or in part on the entry Timpani in Flexikon , a wiki of the DocCheck company . The takeover took place on July 10, 2004 under the then valid GNU license for free documentation .