92 SPECIAL ANA TOMY OF THE SKELETON 



(rostrum sphenoidal is), which is continuous with the sphenoidal crest on the 

 anterior surface, and is received into a deep fissure between the alse of the vomer. 

 On each side may be seen a projecting lamina of bone, the vaginal process (pro- 

 cessus vaginalis), which runs horizontally inward from near the base of the ptery- 

 goid process and articulates with the edges of the vomer. Close to the root of 

 the pterygoid process is a groove (sulcus pterygopalatinus), formed into a com- 

 plete canal when articulated with the sphenoidal process of the palate bone; it 

 is called the pterygopalatine canal, and transmits the pterygopalatine vessels 

 and a pharyngeal branch of the sphenopalatine ganglion. 



The Greater or Temporal Wings (aloe magna}. The greater wings are two 

 strong processes of bone which arise from the sides of the body, and are curved 

 in a direction upward, outward, and backward, each being prolonged behind 

 into a sharp-pointed extremity, the alar, or sphenoidal spine (spina angularis). 

 Each wing presents three surfaces and a circumference. 



Surfaces. The superior surface (Jades cerebralis) (Fig. 56) forms part of 

 the middle fossa of the skull; it is deeply concave, and presents eminences and 

 depressions for the convolutions of the cerebrum. At its anterior and internal 

 part is seen a circular aperture, the foramen rotundum, for the transmission of 

 the second division of the trigeminal nerve. Behind and external to this is a 

 large oval foramen, the foramen ovale, for the transmission of the third division 

 of the trigeminal nerve, the small meningeal artery, and sometimes the small 

 petrosal nerve. At the inner side of the foramen ovale a small aperture may 

 occasionally be seen opposite the root of the pterygoid process; it is the foramen 

 Vesalii, transmitting a small vein. In the posterior angle, near to the spine of 

 the sphenoid, is a short canal, sometimes double, the foramen spinosum, which 

 transmits the middle meningeal artery. Just to the inner side of the foramen 

 spinosum a minute foramen (canaliculus innominatum) is occasionally found, 

 for the passage of the small petrosal nerve. 



The external surface (Fig. 57) is convex and divided by a transverse ridge, 

 the pterygoid ridge (crista infratemporalis), into two portions. The superior 

 or larger, convex from above downward, concave from before backward, enters 

 into the formation of the temporal fossa, and gives attachment to part of the 

 Temporal muscle. The inferior portion, smaller in size and concave, enters 

 into the formation of the zygomatic fossa, and affords attachment to the External 

 pterygoid muscle. It presents, a% its posterior part, a sharp-pointed eminence 

 of bone, the spine, to which are connected the internal lateral ligament of the 

 mandible and the Tensor palati muscle. At its inner and anterior extremity is 

 a triangular spine of bone, which serves to increase the extent of origin of the 

 External pterygoid muscle. 



The anterior surface is divided into two parts, the orbital surface above and the 

 sphenomaxillary below. The orbital surface is quadrilateral in form; it looks 

 inward and forward, and assists in forming the outer wall of the orbit. It 

 is bounded above by a serrated edge for articulation with the frontal bone. 

 Internally this edge is sharp and free and forms the lower boundary of the 

 sphenoidal fissure. At about the centre of the free part of this border a little 

 tubercle projects, giving origin to one head of the External rectus muscle of the 

 eyeball. At its outer part is a notch for the transmission of a recurrent branch 

 of the lacrimal artery. The outer border is serrated for articulation with the 

 malar bone. The lower border is rounded and enters into the formation of the 

 sphenomaxillary fissure. This border separates the orbital surface above from 

 the sphenomaxillary portion below. This latter portion is situated just above 

 the pterygoid process and helps to form the posterior wall of the sphenomaxillary 

 fossa in the articulated skull and exhibits the anterior extremity of the foramen 

 rotundum. 



