The greater wings of the sphenoid are two strong processes of bone, which arise from the sides of the body, and are curved upward, laterally, and backward; the posterior part of each projects as a triangular process that fits into the angle between the squamous and the petrous part of the
temporal bone and presents at its apex a downward-directed process, the
spine of sphenoid bone.
Cerebral surface The
superior or
cerebral surface of each greater wing [Fig. 1] forms part of the middle cranial fossa; it is deeply concave, and presents depressions for the convolutions of the
temporal lobe of the brain. It has a number of foramina (holes) in it: • The
foramen rotundum is a circular aperture at its anterior and medial part; it transmits the
maxillary nerve. • The
foramen ovale is behind and lateral to this; it transmits the
mandibular nerve, the
accessory meningeal artery, and sometimes the
lesser petrosal nerve. • The
sphenoidal emissary foramen is occasionally present; it is a small aperture medial to the foramen ovale, opposite the root of the pterygoid process; it opens below near the
scaphoid fossa, and transmits a small vein from the cavernous sinus. • The
foramen spinosum, in the posterior angle near to and in front of the spine; it is a short canal that transmits the
middle meningeal vessels and a
recurrent branch from the
mandibular nerve. • The
foramen petrosum, a small occasional opening, between the foramen spinosum and foramen ovale, for transmission of the
lesser petrosal nerve.
Lateral surface The
lateral surface [Fig. 2] is convex, and divided by a transverse ridge, the
infratemporal crest, into two portions. • The superior
temporal surface, convex from above downward, concave from before backward, forms a part of the
temporal fossa, and gives attachment to the
temporalis; • the inferior
infratemporal surface, smaller in size and concave, enters into the formation of the
infratemporal fossa, and, together with the infratemporal crest, serves as an attachment to the
lateral pterygoid muscle. It is pierced by the
foramen ovale and
foramen spinosum, and at its posterior part is the
sphenoidal spine, which is frequently grooved on its medial surface for the
chorda tympani nerve. To the sphenoidal spine are attached the
sphenomandibular ligament and the
tensor veli palatini muscle. Medial to the anterior extremity of the infratemporal crest is a triangular process that serves to increase the attachment of the
lateral pterygoid muscle; extending downward and medialward from this process on to the front part of the lateral pterygoid plate is a ridge that forms the anterior limit of the infratemporal surface, and, in the articulated skull, the posterior boundary of the
pterygomaxillary fissure.
Orbital surface The
orbital surface of the great wing [Fig. 2], smooth, and quadrilateral in shape, is directed forward and medially and forms the posterior part of the lateral wall of the orbit. • Its upper serrated edge articulates with the orbital plate of the
frontal bone. • Its inferior rounded border forms the postero-lateral boundary of the
inferior orbital fissure. • Its medial sharp margin forms the lower boundary of the
superior orbital fissure and has projecting from about its center a little tubercle that gives attachment to the inferior head of the
lateral rectus muscle; at the upper part of this margin is a notch for the transmission of a recurrent branch of the
lacrimal artery. • Its lateral margin is serrated and articulates with the
zygomatic bone. • Below the medial end of the superior orbital fissure is a grooved surface, which forms the posterior wall of the
pterygopalatine fossa, and is pierced by the
foramen rotundum.
Margin Commencing from behind [Fig. 2], that portion of the circumference of the great wing that extends from the body to the spine is irregular. • Its
medial half forms the anterior boundary of the
foramen lacerum, and presents the posterior aperture of the
pterygoid canal for the passage of the corresponding nerve and artery. • Its
lateral half articulates, by means of a
synchondrosis, with the petrous portion of the temporal, and between the two bones on the under surface of the skull, is a furrow, the
sulcus of the auditory tube, for the lodgement of the cartilaginous part of the
auditory tube. In front of the spine the circumference presents a concave, serrated edge, bevelled at the expense of the inner table below, and of the outer table above, for articulation with the squamous part of the
temporal bone. At the tip of the great wing is a triangular portion, bevelled at the expense of the internal surface, for articulation with the sphenoidal angle of the
parietal bone; this region is named the
pterion. Medial to this is a triangular, serrated surface, for articulation with the
frontal bone; this surface is continuous medially with the sharp edge that forms the lower boundary of the
superior orbital fissure, and laterally with the serrated margin for articulation with the
zygomatic bone.
Development The greater wing of the sphenoid bone starts as a separate bone, and is still separate at birth in humans. ==Function==