224 Anatomy of Skeleton 



sinus runs, deep to the dura, to reach the cavernous sinus ; a rough front border that 

 articulates with the frontal ; a smooth lower surface which forms the upper boundary 

 of the sphenoidal fissure and, in front of this, the extreme back and inner part of the 

 roof of the orbital cavity. 



The posterior margin is continued into the anterior clinoid process, and the widened 

 wing is attached here by two " roots," which enclose the optic foramen between them. 

 The orbital muscles arise from the front and lower surface of the wing round the anterior 

 opening of the optic foramen. 



The Pterygoid Processes each inner process is fused along its front and upper 

 part with the corresponding outer process, but they are separate below. They diverge 

 from each other behind, the plane of the inner plate being practically parallel with 

 that of its fellow, whereas that of the outer plate is nearly at a right angle with the plane 

 of the outer plate of the opposite side. The deep interval thus left between the inner 

 and outer plates behind is termed the inter-pterygoid or pterygoid fossa : its floor is 

 completed below by the tuberosity of the palate bone, which articulates with the front of 

 the two plates in their lower halves and thus closes the gap that exists here between them 

 in the separated bone. A small area is cut off from the upper or proximal part of the 

 pterygoid fossa by an oblique ridge, and constitutes the scaphoid fossa : the front part 

 of the Tensor palati arises here, and its area of origin extends from this backwards and 

 outwards along the margin of the great wing internal to the foramina, nearly as far 

 as the spine of the sphenoid (Fig. 182). Otherwise the pterygoid fossa is occupied by 

 the Internal Pterygoid muscle, which arises from the inner side of the outer plate 

 and from the tuberosity of the palate between the plates. The External Pterygoid 

 takes origin from the outer side of the outer plate, an area continuous with that on the 

 basal surface of the great wing. Thus the external plate may be looked on as a 

 muscular process, probably developed only in association with such function ; but 

 the inner plate is a bone developed in the pharyngeal wall and only gives origin to one 

 muscle, the upper Constrictor of the pharynx, which arises from the lower half of its 

 posterior border. It is covered by mucous membrane on its inner surface, where it 

 forms the outer wall of the posterior opening of the nasal fossa, and its outer surface 

 is in relation with Internal Pterygoid and Tensor palati, but does not give origin 

 to them. Its lower end is prolonged into a hooked hamular process directed backwards 

 and outwards and showing a deep notch on its outer and front aspect, round wlrch 

 the tendon of Tensor palati turns in to enter the soft palate. 



The posterior margin of the inner plate has the Constrictor arising from its lower 

 half ; above this the pharyngeal end of the cartilaginous Eustachian tube rests against 

 the border just external to the pharyngeal opening, and is fastened here by a strong 

 fascia ; the small Eustachian spine on the border marks the junction of the tubal 

 and constrictor regions. 



A projection, more or less prominent, on the posterior edge of the outer plate a little way down, 

 may mark the anterior attachment of a " pterygo-spinous " ligament extending to the base of the 

 sphenoidal spine. The ligament may be short, fastened higher up on the plate, or two ligaments, 

 long and short, may be present : ossification may extend some way into these, so that a bony bar 

 may be present here. The nerves issuing from the foramen ovale have varying relations with these 

 bands, which are probably modified fibres of the external pterygoid muscle. 



1\i& front border of the inner plate, thick below, is in articulation with the vertical 

 plate of the palate bone ; it turns in under the body of the sphenoid, and here it is 

 interrupted by a groove that marks the ptery go-palatine canal. The inner side of the 

 plate here has the projection of the vaginal process, which receives, between it and the 

 body, the ala of the vomer (Fig. 183). 



