48 ATLAS AND TEXT-BOOK OF HUMAN ANATOMY. 



Fig. 53. — The sphenoid bone seen from in front (|). 

 Fig. 54. — The sphenoid bone seen from behind (|). 



which is completely divided into two portions by a sagittal septum which is rarely situated 

 exactly in the median line. The two sinuses communicate with the posterior superior portion 

 of the nasal fossae by means of irregular openings in the anterior surface of the body of the sphenoid 

 bone (Fig. 53). The greater portion of the almost rectangular anterior surface of the body 

 (Figs. 52 and 53) is formed by two thin, approximately triangular bony platelets, the sphenoidal 

 turbinated bones {concha sphenoidale s), which, although usually united with the sphenoid, are 

 to be regarded as portions of the ethmoid; they are frequently continuous with the ethmoid 

 and may be represented by a number of small independent bones {ossa Bertini). They 

 form the inferior margins of the apertures of the sphenoidal sinuses, and in the neighborhood 

 of the apertures some small fossae which close in the posterior ethmoidal cells are frequently 

 visible. 



The anterior extremity of the septum of the sinuses appears upon the anterior surface of 

 the body of the sphenoid in the shape of a low ridge, the sphenoidal crest (Fig. 53). It is con- 

 tinued upon the lower surface of the body of the sphenoid, where it becomes more pronounced 

 and forms the sphenoidal rostrum, to which is attached the ala vomeris. 



The upper surface of the body (Figs. 43, 44, and 51) is the most strongly marked surface 

 of the bone. Its most striking structure is the so-called sella turcica (see also page 41), which 

 is that portion of the upper surface of the body which belongs to the middle cranial fossa, smaller 

 portions of the body helping in the formation of the floors of the anterior and of the posterior 

 fossae. The portion in the anterior fossa is a plane surface in front of the sella turcica, con- 

 necting the two lesser wings, and is called the jugum sphenoidale; toward the adjacent lamina 

 cribrosa of the ethmoid bone it presents a process, the ethmoidal spine (Fig. 51), the shape of 

 which varies greatly in different individuals. 



Behind the jugum sphenoidale at the anterior margin of the sella turcica there is a shallow 

 groove, the optic groove {sulcus chiasmatis), so called because it contains the decussation or 

 chiasma of the optic nerves (Fig. 51). It is continued on either side into trje optic foramen, 

 which leads into the orbital cavity. 



Behind the optic groove the body of the sphenoid presents a flat elevation, the olivary emi- 

 nence {tuber culum sella:), the margins of which sometimes give origin to the inconstant middle 

 clinoid processes, and between the eminence and the high back of the saddle, the dorsum sella, 

 there is situated a rather deep, slightly elliptical depression, the hypophyseal fossa, which lodges 

 the pituitary body or hypophysis. On each side of this fossa there is upon the root of the greater 

 wing of the sphenoid a shallow but rather broad groove, situated at the junction of the upper 

 and lateral surfaces of the body of the sphenoid bone and limited externally toward the greater 

 wing of the sphenoid by a fine bony platelet, the lingula (Fig. 51). This groove is called the 

 carotid groove (Fig. 54), since it lodges the internal carotid artery. 



The dorsum sellae bears upon either side slightly pointed sharp corners, the posterior clinoid 

 processes. Behind the dorsum sellae a portion of the clivus also belongs to the body of the sphenoid 



