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The average distance between the opening of the stylomastoid foramen and the styloid process is around 0.7 mm or 0.8 mm in adults, but may decrease to around 0.2 mm during aging. [1] The stylomastoid foramen transmits the facial nerve, [2] [3] and the stylomastoid artery. [3] These 2 structures lie directly next to each other. [3]
The mastoid process is located posterior and inferior to the ear canal, lateral to the styloid process, and appears as a conical or pyramidal projection. It forms a bony prominence behind and below the ear. [1] It has variable size and form (e.g. it is larger in the male than in the female). It is also filled with sinuses, or mastoid cells.
The mastoid portion is at first flat, with the stylomastoid foramen and rudimentary styloid immediately behind the tympanic ring. With air cell development, the outer part of the mastoid component grows anteroinferiorly to form the mastoid process, with the styloid and stylomastoid foramen now on the under surface.
The mastoid foramen is a hole in the posterior border of the temporal bone of the skull. [1] The opening of the mastoid foramen is an average of 18 mm from the asterion, [2] and around 34 mm from the external auditory meatus. [3] It is typically very narrow. [1] [3] This may be around 2 mm. [3]
The styloid process is a slender and pointed bony process of the temporal bone projecting anteroinferiorly from the inferior surface of the temporal bone [1] just below the ear. [citation needed] Its length normally ranges from just under 3 cm to just over 4 cm. It is usually nearly straight, but may be curved in some individuals. [1]
The proximal portion of the facial canal is termed the horizontal part.It commences at the introitus of facial canal at the distal end of the internal auditory meatus. The horizontal part is further subdivided into two crura: the proximal/medial [4] anterolaterally [5] directed medial crus (or labyrinthine segment [5]), and the distal/lateral [4] posterolaterally [5] directed lateral crus (or ...
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.
In the lateral part of the jugular fossa of the temporal bone is the mastoid canaliculus for the entrance of the auricular branch of the vagus nerve. Additional images