112 SPECIAL ANATOMY OF THE SKELETON 



which enclose a hollow cellular cavity, and is connected with the perpendicular 

 plate by a narrow, constricted neck. Of these five surfaces, three are articular, 

 two nonarticular or free surfaces. The three articular are the anterior or maxillary 

 surface, which is directed forward, outward, and downward, is. of an oblong form, 

 and rough for articulation with the maxilla. The posterior or sphenoidal surface is 

 directed backward, upward, and inward. It ordinarily presents a small, open cell, 

 the orbital sinus (sinus orbitalis), which communicates with the sphenoidal cells, and 

 the margins of which are serrated for articulation with the vertical part of the sphe- 

 noidal turbinated process. The internal or ethmoidal surface is directed inward, 

 upward, and forward, and articulates with the lateral mass of the ethmoid bone. 

 In some cases the cellular cavity opens on the internal surface of the bone; it then 

 communicates with the posterior ethmoidal cells. More rarely it opens on both 

 surfaces, and then communicates with both the posterior ethmoidal and the 

 sphenoidal cells. The nonarticular or free surfaces are the superior or orbital 

 surface, directed upward and outward, of triangular form, concave, smooth, and 

 forming the back part of the floor of the orbit; and the external or zygomatic 

 surface, directed outward, backward, and downward, of an oblong form, smooth, 

 lying in the sphenomaxillary fossa, and looking into the zygomatic fossa. The 

 latter surface is separated from the orbital by a smooth, rounded border, which 

 enters into the formation of the sphenomaxillary fissure. 



The sphenoidal process (processus spJienoidalis) of the palate bone is a thin, com- 

 pressed plate, much smaller than the orbital, and directed upward and inward. 

 It presents three surfaces and two borders. The superior surface, the smallest 

 of the three, articulates with the under surface of the sphenoidal turbinated pro- 

 cess; it presents a groove, which contributes to the formation of the pterygopala- 

 tine canal. The internal surface is concave, and forms part of the outer wall of 

 the nasal fossa. The external surface is divided into an articular and a nonartic- 

 ular portion; the former is rough, for articulation with the inner surface of the 

 internal pterygoid plate of the sphenoid; the latter is smooth, and forms part of 

 the sphenomaxillary fossa. The anterior border forms the posterior boundary of 

 the sphenopalatine notch. The posterior border, serrated at the expense of the 

 outer table, articulates with the inner surface of the internal pterygoid plate. 



The orbital and sphenoidal processes are separated from each other by a deep 

 notch, the sphenopalatine notch (incisura sphenopalatina), which is converted into 

 a foramen, the sphenopalatine foramen (foramen splienopalatinum), by articulation 

 with the under surface of the body of the sphenoid bone. Sometimes the two pro- 

 cesses are united above, and form between them a complete foramen (Figs. 79 

 and 80), or the notch is crossed by one or more spiculse of bone, so as to form 

 two or more foramina. In the articulated skull this foramen is seen to pass from 

 the sphenomaxillary fossa into the back part of the superior meatus. It trans- 

 mits the sphenopalatine vessels a.nd the superior nasal and nasopalatine nerves. 



Development. From a single centre, which makes its appearance in membrane about the 

 second month at the angle of junction of the two plates of the bone. From this point ossification 

 spreads inward to the horizontal plate, downward into the tuberosity, and upward into the vertical 

 plate. In the fetus the horizontal plate is much larger than the vertical, and even after it is 

 fully ossified the whole bone is remarkable for its shortness. 



Articulations. With six bones the sphenoid, ethmoid, maxilla, turbinated, vomer, and 

 opposite palate. 



Attachment of Muscles. To four the Tensor palati, Azygos uvulae, Internal pterygoid, 

 and Superior constrictor of the pharynx. 



