50 ATLAS AND TEXT-BOOK OF HUMAN ANATOMY. 



border, m contact with the zygomatic bone, and a squamosal border* directed toward the tem- 

 poral bone. The most external portion of the greater wing, which is in contact with the parietal 

 bone in the sphenoparietal suture, is known as the parietal angle, and its most posterior, pointed 

 portion, which is directed toward the petrous portion of the temporal bone, is called the spine 

 (Figs. 53 and 54). The cerebral surface is distinctly concave and exhibits the internal orifices 

 of the foramen rotundum, ovale, and spinosum (Fig. 51), the last receiving its name on account 

 of its location in the spine. f It also occasionally shows digitate impressions and cerebral juga 

 (see pages 41 and 61), and a sulcus arteriosus which is continued from the temporal bone. 



The almost plane, slightly concave, quadrangular orbital surface (Figs. 38 and 53) is the 

 smallest of the three surfaces. It forms a portion of the outer wall of the orbit, and in this situ- 

 ation its zygomatic border articulates with the zygomatic bone by means of the sphenozygomatic 

 suture. The sphenomaxillary or inferior orbital fissure separates the greater wing from the 

 maxilla, and at the margin of this fissure, the orbital surface possesses a sharp edge, the orbital 

 crest, which separates it from the sphenomaxillary surface (Fig. 53), a lower portion of the tem- 

 poral surface. In the vicinity of the superior orbital fissure the orbital surface exhibits a bony 

 spine of variable development which is called the spina recti lateralis and is the point of origin 

 for the muscle of the same name. 



The temporal surface (Figs. 39, 40, and 53) is by far the largest of the three surfaces of 

 the greater wing of the sphenoid and is distinctly angulated at the level of the infratemporal 

 crest (see page 39). The almost vertical portion of the temporal surface, situated above this 

 crest, forms a portion of the planum temporale (see page 38), while the portion situated below 

 the crest is divided into the more horizontal infratemporal surface and the triangular spheno- 

 maxillary surface by a rather low ridge which is called the sphenomaxillary ridge. The spheno- 

 maxillary surface (Fig. 53) looks rather anteriorly and overlaps the root of the pterygoid process, 

 while the infratemporal surface is directed more to the side, and presents the external orifices 

 of the foramen ovale and the foramen spinosum. It forms the posterior wall of the pterygo- 

 palatine (sphenomaxillary) fossa (see page 78), and contains the anterior or external orifice of 

 the foramen rotundum. It is sharply separated from the orbital surface by the orbital crest 



(Fig- 53)- 



While the greater and lesser wings of the sphenoid are practically horizontal, the third 



pair of processes, the pterygoid processes (Figs. 53 and 54), pass almost vertically downward 



and are apposed (Figs. 41 and 42) to the posterior surface of the maxilla (see page 67) and to 



the hard palate (see page 79), forming the lateral boundaries of the posterior nares. Each 



pterygoid process arises from the lower surface of the body of the sphenoid by two roots, between 



which is the pterygoid (Vidian) canal (Fig. 53), which runs almost horizontally, its anterior 



extremity being in the pterygopalatine fossa, and its posterior one in the foramen lacerum. 



Below the pterygoid canal the pterygoid process divides into two lamellae, the internal and the 



external pterygoid plate. The internal plate is narrower and almost vertically placed, while 



* So named where it borders upon the squamous portion of the temporal bone; in the region of the sphenopetrosal 

 fissure (see page 39) it is called the petrosal border. 



j Occasionally the foramen spinosum is only partially limited by the sphenoid bone, i. e., it is simply a notch in 

 the spine. 



