| Bone: Greater wing of sphenoid bone | |
|---|---|
| Figure 1: Sphenoid bone, upper surface. | |
| Figure 2: Sphenoid bone, anterior and inferior surfaces. | |
| Latin | ala major ossis sphenoidalis |
| Gray's | subject #35 149 |
The greater wing of the sphenoid bone, or alisphenoid, is a bony process of the sphenoid bone; there is one on each side, extending from the side of the body of the sphenoid and curving upward, laterally, and backwards.
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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 which fits into the angle between the squamous and the petrous part of the temporal bone and presents at its apex a downwardly directed process, the spine of sphenoid bone.
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 lateral surface [Fig. 2] is convex, and divided by a transverse ridge, the infratemporal crest, into two portions.
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 which 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 which forms the anterior limit of the infratemporal surface, and, in the articulated skull, the posterior boundary of the pterygomaxillary fissure.
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.
Commencing from behind [Fig. 2], that portion of the circumference of the great wing which extends from the body to the spine is irregular.
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.
The greater wing of the sphenoid bone starts as a separate bone, and is still separate at birth in humans.
In many mammals, e.g. the dog, the greater wing of the sphenoid bone stays through life a separate bone called the alisphenoid.
This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.