526 ANATOMY IX A NUTSHELL. 



binated, and the vomer. The ethmoid bone with its articulations form the 

 nasal fossa. The two sphenoidal turbinated bones articulate with the ethmoid 

 also. bu1 as they are processes of the sphenoid we do not name them in the 

 articulations of the ethmoid, since the sphenoid itself has been named. 



A i i \< hment of Muscles. — There are no muscles attached to this hone. 



Blood Supply. Aaiterior ethmoidal artery, posterior ethmoidal artery, 

 ami nasal or spheno-palatine branch of internal maxillary artery. 



LESSON CLXXVII. 

 Sphenoid Bone. (Plates CCXLIII-CCXLIV). 



'The sphenoid bone forms most of the middle fossa at the base of the skull. 

 It touches all the hones of the cranium, the vomer, two palate and two malar 

 f the face. Occasionally its external pterygoid plate articulates with the 

 superior maxillary hone. It presents the following points for consideration: 



1. A body, which is a hollow cuboid structure with six surfaces. 



The superior surface has in front THE kthmoidal SPINE which articulates 

 with the cribriform plate of the ethmoid. It then has a smooth surface with 

 a slight longitudinal eminence in the mid-line and on each side of this eminence 

 is a groove for the olfactory tract. The next point is the optic groove, which 

 lodges the optic commissure and ends on each side in thk optic FORAMEN which 

 is for the passage of the optic nerve and the ophthalmic artery. Thk olivary 

 process is immediately behind the optic groove. Thk sklla Turcica (pit- 

 uitary fossa), which is for the pituitary body (hypophysis) of the brain, is just 

 behind the olivary process. Thk middle clinoid processes bound the sella 

 Turcica in front. Thk dorsum skll.k (dorsum ephippii) bounds the sella 

 Turcica behind, and is grooved on each side for the sixth nerve. Thk pos- 

 terior clinoid processes are a1 each upper angle of the dorsum sella?. Grooves 

 are situated laterally on the body for the cavernous sinus and the internal 

 carotid artery. They ate curved like the Italic letter f. Thk lingula is a 

 ridge along the outer margin of this groove posteriori}-. Thk clivus is a shallow 

 depression which lodges the pons and slopes backward from the dorsum sella' 

 to be continuous with the basilar groove of the occipital bone. 



The posterior surface joins the basilar process of the occipital bone. This 



ce is quadrilateral in shape and there is a layer of cartilage between it and 

 the occipital bone until about the twentieth year. 



The anterior surface has in the median line thk ETHMOIDAL CREST. This 

 cresl articulates with the perpendicular plate of the ethmoid. Sphenoidal 



i ELLS or sinuses are on each side of this ethmoidal crest. Thk SPHENOIDAL 

 Ti RBINATED BONE partly closes these cells or sinuses in front and below, but 

 they communicate with the nose and sometimes with the posterior ethmoidal 

 cell.-. This surface articulates with the orbital process of the frontal bone 

 above, and with the orbital process of the palate bone below, and with the os 



plannum of the ethmoid LATERALLY. 



The inferior surface has in its mid-line Tin: ROSTRUM, which articulates 

 with the upper edge of the vomer. Thk vaginal processes are on each side, 

 and articulate with the alae of the vomer. This inferior surface helps to form 





