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It presents, near the labyrinthic wall, a small aperture for the passage of the tympanic branch of the glossopharyngeal nerve. The posterior wall (or mastoid wall) is wider above than below, and presents for examination the entrance to the tympanic antrum, the pyramidal eminence, and the fossa incudis.
The central portion of the tympanic part is thin, as it gives rise to the bony inner two-thirds of the ear canal, and in 5 - 20% of skulls the lower surface is perforated by a hole, the foramen of Huschke [1] that opens onto the temporomandibular joint due to incomplete fusion of the anterior and posterior prominences during development.
The medial wall of the aditus features a ridge created by the underlying facial canal, and a bulge created by the underlying ampulla of the lateral semicircular canal. The short limb of incus is lodged in a shallow fossa upon the posterior wall of the tympanic cavity just inferior to the aditus.
The mastoid antrum (tympanic antrum, antrum mastoideum, Valsalva's antrum) is an air space in the petrous portion of the temporal bone, communicating posteriorly with the mastoid cells and anteriorly with the epitympanic recess of the middle ear via the aditus to mastoid antrum (entrance to the mastoid antrum). These air spaces function as ...
The pyramidal eminence is a hollow conical projection upon the posterior wall of the tympanic cavity of the middle ear. The stapedius muscle arises in the hollow of the eminence and its tendon exits through its apex.
A third (pterotic) roofs in the tympanic cavity and antrum; while the fourth (epiotic) appears near the posterior semicircular canal and extends to form the mastoid process (Vrolik). The tympanic ring is an incomplete circle, in the concavity of which is a groove, the tympanic sulcus, for the attachment of the circumference of the eardrum ...
The mastoid antrum is situated posterior to the recess and opens into the recess at the posterior wall of the recess via the aditus to mastoid antrum. [1]: 416 The ampulla of the lateral semicircular canal creates a prominence upon the medial wall of the recess. [1]: 420
The orifice of the vestibular aqueduct is the hind part of the medial wall; it extends to the posterior surface of the petrous portion of the temporal bone. It transmits a small vein and contains a tubular prolongation of the membranous labyrinth , the endolymphatic duct , which ends in a cul-de-sac between the layers of the dura mater within ...