QS Study

The middle car cavity is a biconcave space with a vertical and anteroposterior diameter of about 15 mm and transverse diametric from 2 mm to 6 mm. It is an irregular air-filled space hollowed out in the center of the temporal bone between the external auditory meatus laterally and the inner ear medially.

Boundary –

The middle car cavity has six walls.

Roof: Roof is formed by tegmen tympani which is a thin plate of bone separating the cavity of the middle cranial fossa.

Floor: It is formed by a thin plate of bone separating the cavity from the cavity of the jugular bulb. It consists of a thin layer of bone, which separates the middle ear from the internal jugular vein.

Lateral wall: It is mainly formal by the tympanic membrane and partly by squamous temporal bone. It is made up of the tympanic membrane and the lateral wall of the epitympanic recess.

Anterior wall: It is very narrow. It separates the middle ear from the internal carotid artery. It has three important structures from above downwards –

  • Wall of the carotid canal.
  • Canal for the tensor tympani muscle.
  • Eustachian tube orifice (Auditory tube).

Medial wall: If separates the middle ear from the inner ear. The most obvious feature is the promontory. Below and behind the promontory is the fenestra rotunda closed by the secondary tympanic membrane.

Posterior wall: It is formed by a deeper part of the posterior tympanum containing descending part of the facial nerve. It presents the aditus to the mastoid antrum.

Middle Ear Cavity 1

Contents –

The middle ear cavity contains the followings:

  • Three small ossicles -malleus, incus, and stapes.
  • Ligaments of the car ossicles.
  • Two muscles: the tensor tympani and the stapedius.
  • Vessels supplying and draining the middle ear.
  • Nerves: Chorda tympani and tympanic plexus.

The mucous membrane lining the middle car cavity partitions all the contents and forms several vascular folds which project into the cavity.

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