Bones of the Skull. 



Ala parva 



t 



Corpus 



Angulus / 

 parietalis 



Sulcus chiasmatis 



' /Tuberculum sellae 

 / Sella turcica 



' /Foramen opticum 



' Processus y* 



clinoideus xV 



X 



Margo squamosus 



" "Fissura orbitalis superior 

 Processus clinoideus anterior 

 ~" Foramen rotundum 

 - - Facics cerebralis 



Processus clinoideus posterior 

 Foramen ovale 

 Foramen spinosum 



Lingula sphenoidalis 



Ala 



4, Sphenoid bone, os sphenoidale, from above. 



The unpaired OS spheiioidale (see also Figs. 5, 6, 55, 56, 59, 60, 6371) lies in the 

 middle of the base of the skull. It is divisible into a middle piece or body (corpus) and six 

 processes, known as the two small wings or alae parvae ; the two large wings or alae magnae, 

 and the two pterygoid processes or processus pteryyoidei ; of these the four former are directed 



lateralward, the two latter, downward. 



The corpus (body) (see also Figs. 5, 6, 59, 60, 6366, 68) is approximately cubical 

 and contains within it two cavities lined by mucous membrane, the sinus sphenoidales (0. T. 

 sphenoidal cells) which are separated from one another by the septum sinuum sphenoidalium. 

 The superior surface presents a deep frontally placed groove, the sella turcica (for the sinus 

 circularis; hypophysis) with the fossa hypophyseos (0. T. pituitary fossa) in the depth. 

 Posteriorly, the sella is overhung by the dorsum sellae, which at the angles of its upper free 

 margin presents on each side a small processus clinoideus posterior (for the tentorium cere- 

 belli) ; the posterior smooth surface of the dorsum sellae, together with the superior surface of 

 the pars basilaris oss. occipitalis, forms the clivus (for the aa. vertebrates, a. basilaris and its 

 branches; pons). In front of the sella lies the small tuberculum sellae or pommel; lateral- 

 ward and backward therefrom are situated the middle clinoid processes or processus clinoidei 

 medii (often absent). In front of the tubercle, extending transversely on each side to the 

 foramen opticum , is the shallow sulcus chiasmatis (0. T. optic groove) behind which lies the 

 chiasma opticum. The anterior margin of the ^ superior surface unites with the lamina cribrosa 

 of the ethmoid bone to form the sutura sphenocthmoidalis. On the lateral surface extending 

 from behind forward , above the region of origin of the large wing is the sulcus caroticus 

 (0. T. cavernous groove) for the a. carotis interna and the plexus caroticus interims. Just 

 lateralward from the posterior extremity of this sulcus projects the linyula sphenoidalis. The 

 posterior surface of the body unites with the pars basilaris oss. occipitalis (see p. 1). The 

 anterior, and a part of the inferior, surface are formed by the thin, saucer -shaped, curved 

 conchae sphenoidales (0. T. sphenoidal turbinated bones) which, embryologically, properly belong 

 to the ethmoid bone. Each presents lateralward and above an opening, the apertura sinus 

 sphenoidalis and, lateralward from this, small depressions which form the posterior walls of 

 the posterior ethmoidal cells; the lateral border of each concha is connected above with the 

 lamina papyr. oss. ethmoid, (sutura sphenoethmoidalis) ; below with the--prtrtr-ofbit-_Qas^-palat. 

 (sutura sphenoorbitalis) . In the median plane the conchae and the septum in front form the 

 projecting sphenoidal crest or^crista sphenoidalis (0. T. ethmoidal crest) for contact with the 

 perpendicular plate of the ethmoid bone; this crest runs out below into a projection, the 

 rostrum sphenoidale which is directed downward and lies against the vomer. 



