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fossa cranii media
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Base of the skull Upper surface (Middle cranial fossa is the centermost of the three indentations, in pink and yellow)
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The , deeper than the
Anterior Cranial Fossa , is narrow in the middle, and wide at the sides of the
Skull .
It is bounded in front by the posterior margins of the small wings of the
Sphenoid , the anterior clinoid processes, and the ridge forming the anterior margin of the
Chiasmatic Groove ; behind, by the superior angles of the petrous portions of the temporals and the
Dorsum Sellæ ; laterally by the temporal squamæ, sphenoidal angles of the parietals, and great wings of the sphenoid. It is traversed by the squamosal, sphenoparietal, sphenosquamosal, and sphenopetrosal sutures.
The middle part of the fossa presents, in front, the
Chiasmatic Groove and
Tuberculum Sellæ ; the chiasmatic groove ends on either side at the
Optic Foramen , which transmits the
Optic Nerve and
Ophthalmic Artery to the
Orbital Cavity .
Behind the optic foramen the
Anterior Clinoid Process is directed backward and medialward and gives attachment to the
Tentorium Cerebelli .
Behind the tuberculum sellæ is a deep depression, the
Sella Turcica , containing the
Fossa Hypophyseos , which lodges the
Hypophysis , and presents on its anterior wall the
Middle Clinoid Processes .
The .
On either side of the sella turcica is the
Carotid Groove , which is broad, shallow, and curved somewhat like the italic letter ''f''.
It begins behind at the
Foramen Lacerum , and ends on the medial side of the anterior clinoid process, where it is sometimes converted into a foramen (carotico-clinoid) by the union of the anterior with the middle clinoid process; posteriorly, it is bounded laterally by the
Lingula .
This groove lodges the
Cavernous Sinus and the
Internal Carotid Artery , the latter being surrounded by a plexus of
Sympathetic Nerves .
The lateral parts of the middle fossa are of considerable depth, and support the
Temporal Lobes of the
Brain .
They are marked by depressions for the brain convolutions and traversed by furrows for the anterior and posterior branches of the
Middle Meningeal Vessels .
These furrows begin near the
Foramen Spinosum , and the anterior runs forward and upward to the sphenoidal angle of the parietal, where it is sometimes converted into a bony canal; the posterior runs lateralward and backward across the
Temporal Squama and passes on to the parietal near the middle of its lower border.
The following apertures are also to be seen.
In front is the
Superior Orbital Fissure , bounded above by the small wing, below, by the
Great Wing , and medially, by the body of the
Sphenoid ; it is usually completed laterally by the
Orbital Plate of the
Frontal Bone .
It transmits to the
Orbital Cavity the
Oculomotor , the
Trochlear , the
Ophthalmic Division of the
Trigeminal , and the
Abducent Nerves , some filaments from the
Cavernous Plexus of the sympathetic, and the orbital branch of the
Middle Meningeal Artery ; and from the orbital cavity a recurrent branch from the
Lacrimal Artery to the
Dura Mater , and the
Ophthalmic Veins .
Behind the medial end of the
Superior Orbital Fissure is the
Foramen Rotundum , for the passage of the
Maxillary Nerve .
Behind and lateral to the foramen rotundum is the
Foramen Ovale , which transmits the
Mandibular Nerve , the
Accessory Meningeal Artery , and the
Lesser Superficial Petrosal Nerve .
Medial to the foramen ovale is the
Foramen Vesalii , which varies in size in different individuals, and is often absent; when present, it opens below at the lateral side of the
Scaphoid Fossa , and transmits a small vein.
Lateral to the foramen ovale is the
Foramen Spinosum , for the passage of the middle meningeal vessels, and a recurrent branch from the mandibular nerve.
Medial to the foramen ovale is the
Foramen Lacerum ; in the fresh state the lower part of this aperture is filled up by a layer of
Fibrocartilage , while its upper and inner parts transmit the
Internal Carotid Artery surrounded by a plexus of sympathetic nerves.
The nerve of the
Pterygoid Canal and a meningeal branch from the
Ascending Pharyngeal Artery pierce the layer of fibrocartilage.
On the anterior surface of the petrous portion of the temporal bone are seen the eminence caused by the projection of the
Superior Semicircular Canal ; in front of and a little lateral to this a depression corresponding to the roof of the
Tympanic Cavity ; the groove leading to the hiatus of the
Facial Canal , for the transmission of the
Greater Superficial Petrosal Nerve and the petrosal branch of the
Middle Meningeal Artery ; beneath it, the smaller groove, for the passage of the
Lesser Superficial Petrosal Nerve ; and, near the apex of the bone, the depression for the
Semilunar Ganglion and the orifice of the carotid canal.
