90 



SPECIAL ANATOMY OF THE SKELETON 



The Body (corpus), The body is of large size and hollowed out in its interior 

 so as to form a mere shell of bone. It presents for examination four surfaces 

 a superior, an inferior, an anterior, and a posterior. 



Surfaces. The superior surface (fades cerebralis) (Fig. 56) presents in front 

 a prominent spine, the ethmoidal spine, for articulation with the cribriform plate 

 of the ethmoid; behind this is a smooth surface having in the median line a slight 

 longitudinal eminence, with a depression on each side for the lodgement of the 

 olfactory lobes. This surface is bounded behind by a ridge, which forms the 

 anterior border of a narrow, transverse groove, the optic groove (sulcus chiasmatis); 

 behind the ridge lies the optic chiasm; the groove is continuous on each side with the 

 optic foramen (foramen opticum), for the passage of the optic nerve and ophthalmic 

 artery. Behind the optic groove is a small eminence, olive-like in shape, the 



Middle chnoid process. Ethmoidal 



^Posterior dinoid process.^ \ GnmefiH . V 

 olfactory 



Optic foramen. 

 Sphenoidal fissure: 



Foramen rotundum. 



Foramen Vesalii: 



Foramen ovale: 



Foramen spinosum. 



FIG. 56 Sphenoid bone. Superior surface. 



olivary eminence (tuberculum sellae); and still more posteriorly a deep depression, 

 the sella turcica (fossa hypophyseos), which lodges the circular sinus and the 

 hypophysis. This fossa is perforated by numerous foramina, for the transmission 

 of nutrient vessels into the substance of the bone. It is bounded in front by the 

 olivary eminence, and also by two small processes, one on either side, called the 

 middle clinoid processes (processus clinoidei medii), which are sometimes connected 

 by a spiculum of bone to the anterior clinoid processes. It is bounded behind by 

 a square-shaped plate of bone, the dorsum sellae, terminating at each superior 

 angle in a tubercle, the posterior clinoid process (processus clinoideus posterior). 

 The size and form of these processes vary considerably in different individuals. 

 They deepen the sella turcica, and serve for the attachment of prolongations 

 from the tentorium eerebelli. The sides of the dorsum sellae are notched for 

 the passage of the abducent nerves, and below present a sharp process, the 

 petrosal process, which is joined to the apex of the petrous portion of the temporal 

 bone, forming the inner boundary of the middle lacerated foramen. Behind 

 this plate the bone presents a shallow depression, which slopes obliquely backward, 

 and is continuous with the basilar groove of the occipital bone; it is called the 

 clivus, and supports the upper part of the pons. On either side of the body is 

 a broad, /-shaped groove, which lodges the internal carotid artery and the 

 cavernous sinus; it is called the carotid or cavernous groove (sulcus caroticus). 



