The middle ear or tympanic cavity
The middle ear or tympanic cavity is an irregular, laterally compressed space within the temporal bone. It is filled with air, which is conveyed to it from the nasal part of the pharynx through the auditory tube. It contains a chain of movable bones, which connect its lateral to its medial wall, and serve to convey the vibrations communicated to the tympanic membrane across the cavity to the internal ear.
The tympanic cavity consists of two parts: the tympanic cavity proper, opposite the tympanic membrane, and the attic or epitympanic recess, above the level of the membrane; the latter contains the upper half of the malleus and the greater part of the incus. Including the attic, the vertical and antero-posterior diameters of the cavity are each about 15 mm. The transverse diameter measures about 6 mm. above and 4 mm. below; opposite the center of the tympanic membrane it is only about 2 mm. The tympanic cavity is bounded laterally by the tympanic membrane; medially, by the lateral wall of the internal ear; it communicates, behind, with the tympanic antrum and through it with the mastoid air cells, and in front with the auditory tube
The Tegmental Wall or Roof (paries tegmentalis) is formed by a thin plate of bone, the tegmen tympani, which separates the cranial and tympanic cavities. It is situated on the anterior surface of the petrous portion of the temporal bone close to its angle of junction with the squama temporalis; it is prolonged backward so as to roof in the tympanic antrum, and forward to cover in the semicanal for the Tensor tympani muscle. Its lateral edge corresponds with the remains of the petrosquamous suture.
The Jugular Wall or Floor (paries jugularis) is narrow, and consists of a thin plate of bone (fundus tympani) which separates the tympanic cavity from the jugular fossa. It presents, near the labyrinthic wall, a small aperture for the passage of the tympanic branch of the glossopharyngeal nerve.Поділитися цим: