1 6 EQUINE ANATOMY. 



SPHENOID. 



The sphenoid (a wedge) serves to connect the bones of the head 

 and face, being wedged in between the occipital behind, the 

 ethmoid and frontal in front, the parietals and temporals laterally. 

 It is divided into a body and two wings. 



The body shows on its internal surface 



The optic fossa, a transverse depression for the optic nerves, 

 ending in the optic foramina, which open into the orbit. 



The sella turcica or pituitary fossa, behind this, receiving the 

 pituitary body. 



The wings projecting from the body -and articulating with the 

 frontal. 



Two fissures outside the sella turcica, the inner one lodging the 

 cavernous sinus. 



The supra-sphenoidal canals, the upper one called the great 

 sphenoidal fissure, the lower the foramen rotundum, the middle 

 opening near the optic. 



The External or Inferior Surface shows 



Outside, the vidian canal opening into the orbit. 



The internal pterygoid plate (pterygoid bone) outside the vomer, 

 flattened laterally. 



Its internal face forms part of the pharyngeal walls. 



At its base is found the vidian canal (see above). 



Its apex forms the hamular (hooked) process, passing back- 

 ward and serving for the passage of the tendon of the tensor palati. 



The external pterygoid or sub-sphenoidal process lying outside 

 the preceding. 



Above this the opening of the sub-sphenoidal canal which opens 

 into the orbit. 



Below two fissures for articulation with the vomer. 



The superior or posterior border is continuous with the basilar 

 process of the occipital, and on each side forms the inner bound- 

 aries of the lacerated foramen. Three notches are also seen, for 

 the passage of the carotid artery, the foramen ovale for the infe- 

 rior maxillary nerve, and one for the middle meningeal artery, the 

 foramen spinosum. 



The anterior or inferior border shows 



The sphenoidal sinuses, excavations continuous with the eth- 

 moidal plate. 



