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Anatomy of tympanic cavity In short detailed

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Tympanic cavity (middle ear)

The tympanic cavity is an air-filled space within the petrous temporal bone, lying between the tympanic membrane laterally and inner ear medially. It transmits sound vibrations from the eardrum to the inner ear through the auditory ossicles.
Labeled middle-ear anatomy showing attic, hypotympanum, Eustachian tube, tympanic membrane, ossicles, mastoid and facial nerve

Divisions

  1. Epitympanum (attic): Part above the level of the tympanic membrane and malleolar folds. It contains the head of malleus and body of incus.
  2. Mesotympanum: Middle part, opposite the tympanic membrane. It contains most of the ossicular chain.
  3. Hypotympanum: Part below the tympanic membrane/tympanic annulus.
  4. Clinically, the anterior part is termed protympanum, continuous with the auditory tube; the posterior recess is the retrotympanum.

Boundaries: six walls

WallMain structures and relations
RoofTegmen tympani, a thin bony plate separating the cavity from the middle cranial fossa and temporal lobe.
FloorThin bone over the jugular bulb in the jugular fossa.
Lateral wallMainly the tympanic membrane; upper bony part is the scutum.
Medial wallSeparates the middle ear from the inner ear. It shows the promontory formed by the basal cochlear turn, oval window occupied by stapes footplate, and round window closed by the secondary tympanic membrane.
Anterior wallRelated to the internal carotid artery. Contains the tympanic opening of the pharyngotympanic (Eustachian) tube and the semicanal for tensor tympani.
Posterior wallCommunicates through the aditus ad antrum with mastoid antrum and air cells. It includes the pyramidal eminence containing stapedius muscle, and is closely related to the facial nerve canal.

Contents

  • Auditory ossicles: malleus, incus and stapes
    • Malleus attaches to tympanic membrane
    • Stapes footplate fits into oval window
  • Muscles
    • Tensor tympani: attached to malleus, supplied by mandibular division of trigeminal nerve
    • Stapedius: attached to stapes, supplied by facial nerve
  • Nerves
    • Chorda tympani crosses the cavity between malleus and incus. It carries taste from anterior two-thirds of tongue and parasympathetic fibers to submandibular and sublingual glands.
    • Tympanic plexus lies on the promontory.
  • Vessels: small tympanic branches of carotid and other regional arteries.
  • The cavity is lined by mucosa and communicates anteriorly with the nasopharynx through the pharyngotympanic tube, which equalizes middle-ear pressure.

Applied anatomy

  • Infection can pass from the nasopharynx through the auditory tube, producing otitis media.
  • The attic is a common site for cholesteatoma.
  • Its close relations to the facial nerve, cochlea, jugular bulb, carotid artery and cranial cavity are important in middle-ear surgery.
The compartmental and wall descriptions above are consistent with Shambaugh Surgery of the Ear and Scott-Brown’s Otorhinolaryngology, including the tegmen tympani roof, jugular-bulb floor, tympanic-membrane lateral wall, and inner-ear medial boundary.
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