528 ANATOMY IN A NUTSHELL. 



at its upper pari for a branch of the lachrymal artery, and a spine at its center 

 which gives origin to one head of the External rectus muscle. 



'I'lic circumference of the greater wing of the sphenoid articulates with 

 the temporal and frontal hones. Tart of its inner portion forms the lower 

 boundary of the sphenoidal fissure and helps to form the foramen lacerum 

 medium. 



3. The lesser wings ni the sphenoid hone (processes of Incrassias) project 

 outward from the upper and lateral part of the body to end in a sharp point. 

 Each wing has two roots; the upper is thin and flat, and the lower is thicker and 

 has near the body a small tubercle to which is attached the ligament of Zinn. 

 Tin; OPTIC FORAMEN which transmits the optic nerve and the ophthalmic artery 

 is between these roots. The anterior border of each wing articulates with the 

 frontal hone, while the posterior border lies in the fissure of Sylvius, and ends 

 in THE INTERIOR CLINOID process internally. Its upper surface is smooth and 

 flat and is situated in the anterior fossa at the base of the skull. The lower 

 surface forms the upper border of the sphenoidal fissure and the hack of the 

 roof of the orbit. Tin-: sphenoidal fissure (anterior lacerated) is hounded 

 above by the lesser wing of the sphenoid, internally by the body of the sphe- 

 noid, and below by the inner margin of the orbital surface of the greater wing 

 of the sphenoid. The following strictures pass through the sphenoidal 

 fissure: the third nerve, fourth nerve, three divisions of the ophthalmic division 

 of the fifth the sixth nerve, filaments from the cavernous plexus of the sympa- 

 thetic, orbital hranches of the middle meningeal artery, the ophthalmic vein, 

 and recurrent branch of the lachrymal artery. 



4. The pterygoid processes of the sphenoid bone descend on either side from 

 the junction of the body witli the greater wing. Each process consists of two 

 plates, external pterygoid plate and internal pterygoid plate, and a pterygoid 

 fossa. Tin: external pterygoid plate forms part of the inner wall of the 

 zygomatic fossa and gives attachment to the External pterygoid muscle, and 

 its inner surface gives attachment to the Internal pterygoid muscle. Tin: 

 internal pterygoid plate is longer and narrower than the external one and 

 has on its extremity the hamular process around which the tendon of the 

 Tensor palati muscle turns. The scaphoid fossa is at the base of the in- 

 ternal pterygoid plate and gives origin to the Tensor palati muscle. The 

 vidian canal is at the loot of the pterygoid process for the vidian nerve and 

 vessels. A triangi lap notch is at the rool of the hamular process to articu- 

 late with the pterygoid process of the palate hone. 



5. The sphenoidal turbinated hones (spongy) articulate in front with the 

 ethmoid ami with the palate externally. They are irregular bones, wide an- 

 teriorly, and tapering posteriorly. 



Ossifn vtion. This bone ossifies from fourteen centers. 

 Articulation. It articulates with twelve hones which are. the two malar, 



the two palate, and the vomer of the lace, and with all the hones of the cranium 

 which are. frontal, ethmoid, two parietal, two temporal, and the occipital. 



Attachment of Mi scles. It has twelve pairs of muscles attached to it. 

 TheTemporal of thetemporo-maxillary region, the External pterygoid and the 



