THE SPHENOID BONE 



53 



noidalis), which overhes the entrance to the optic foramina. The median ridge is 

 termed the ethmoidal spine, since it fits into a notch of the cribriform plate of the 

 ethmoid bone and joins the crista galli. (2) Just behind this and at a lower level 

 is a smooth transverse depression, the optic groove (Sulcus chiasmatis), on which 

 the optic chiasma rests. (3) From each end of this groove the optic foramen 

 (Foramen opticum) passes forward and outward to terminate in the posterior part 

 of the orbital fossa. ^ (4) Near the posterior end is a central depression, the hypo- 

 physeal or pituitary fossa (Fossa hypophyseos), which lodges the hypophysis cerebri 

 or pituitary body. On each side of this is a shallow groove for the internal carotid 

 arterj' and the cavernous sinus. The anterior end is expanded, and joins the eth- 

 moid and palatine bones; it is excavated to form the sphenoidal sinuses. These 

 cavities extend back as far as the optic 

 groove, and are usually continuous in front 

 with the cavities in the vertical parts of the 

 palate bones;- they are separated by a com- 

 plete septum which is not always median. 

 The posterior end is flat and is joined to 

 the basilar part of the occipital; at the line 

 of junction there is dorsally a slight trans- 

 verse elevation, the spheno-occipital crest 

 (Crista spheno-occipitalis) . 



The orbital wings (Alse orbitales) curve 

 dorso-laterally from the. sides of the body of 

 the presphenoid. Their cerebral surface is 

 concave, and is marked by digital impres- 

 sions (Impressiones digitatse) for the gyri 

 of the cerebrum. The lateral surface is con- 

 vex and is largely concealed by the overlap- 

 ping temporal wing and the squamous tem- 

 poral and frontal bones; a narrow part of it 

 (Facies orbitalis) is uncovered on the medial 

 wall of the orbital cavity at the sphenoidal 

 notch of the frontal bone. The dorsal bor- 

 der unites with the frontal bone at the 

 spheno-frontal suture. The anterior border 

 joins the ethmoid at the spheno-ethmoidal 

 suture; at its lower part it concurs with the 

 ethmoid and frontal in the formation of the 

 ethmoidal foramen (Foramen ethmoidale).^ 

 The posterior border is overlapped by the 

 temporal wing and the squamous temporal. 

 The root of the wing is perforated by the 

 optic foramen (Foramen opticum) . Immedi 



ately below and behind the latter (i. e., ben__ i + ;„ „ 



Below this, and separated from it usually by a thin and often mcomplete plate, s a 

 larger opening, the foramen rotundum, which is bounded externally by the root of 



''"" ^heTrnporal'^ngs (Al. temporales) extend outward and somewhat upward 

 from the body of the postsphenoid; they are smaller than the orbital wmgs and 



1 This foramen might well be called a canal, since it is an inch or more in length 



ment exists in about a third of the cases accordmg to Faulli. 

 3 Also called the internal orbital foramen. 



Fig. 31. — Sphenoid Bone and Basilar Paht of 

 Occipital Bone of New-born Foal; Dorsal 

 View. 



C, Body of presphenoid; C, body of postsphe- 

 noid; B.O., basilar part of occipital bone; A.o., orbital 

 wing of sphenoid bone; .-l.(., temporal wing of sphe- 

 noid bone; 1, 1, optic foramina; 2, optic groove; 3, 

 hypophyseal fossa; 4, 5, grooves; 6, ethmoidal 

 notch; 7, ethmoidal spine; 8, junction with crib- 

 riform plate' of ethmoid bone; 9, junction with 

 frontal bone; 10, junction with squamous temporal 

 bone; 11, margin of foramen lacerum anterius; 12, 

 spheno-occipital crest; 13, junction of basilar part 

 of occipital bone with lateral part. 



beneath the root) is the foramen orbitale. 



