Bones of the Skull. 



17 



Glabella 

 Spina frontalis 



Fovea 

 trochlearis 



Incisura 

 ethmoiclalis 



Arcus superciliaris 

 Incisura frontalis 

 Spina trochlearis 



Foramen supraorbitale 

 Margo supraorbitalis 

 Fossa glandulae 

 lacrimalis 



Pars orbitalis 



Processus zygomaticus 



Facies orbitalis 

 Foramen ethmoidale anterius 

 v Foramen ethmoidale posterius 



18. Frontal bone, os frontale, from below. 



The partes orbitales (see also Figs. 17, 63 66 and 68 71) pass at a right angle 

 from the inferior margin of the squama frontalis backward and are separated from one another 

 by the quadrangular incisura ethmoidalis cutting in from behind. The anterior boundary is 

 formed by the marfjo supraorbitalis; the lateral by the processes zygomaticus. The posterior 

 margin is slightly serrated medianward for union with the ala parva oss. sphenoid., and is 

 continuous lateralward toward the proc. zygomat. with a triangular rough surface for contact 

 with the margo frontalis of the ala magna oss. sphenoid, (sutura sphenofrontalis) ; behind this 

 surface lies a variable, narrow, sickle-shaped, smooth field, which along with the ala parva oss. 

 sphenoid, helps to form the middle fossa of the skull. The medial border, bounding the incisura 

 ethmoidalis, is only slightly rough and forms with the lateral margin of the lamina cribrosa 

 oss. ethmoid, a part of the sutura frontoethmoidalis. Parallel to this margin a rough ridge 

 runs lateralward to which are attached in front the os lacrimale by the sutura frontolacrimalis, 

 behind the lamina papyracea oss. ethmoid, by a part of the sulura frontoethmoidalis. The 

 oblong field lying between this ridge and the medial border is irregularly divided by thin 

 transverse ridges, lies upon the upper surface of the ethmoidal labyrinth and presents bulgings 

 due to the cellulae ethmoidales which extend into it; two grooves, running frontally, form with 

 corresponding grooves of the ethmoidal labyrinth the foramen ethmoidale anterius (for the 

 a. ethmoid, ant. ; n. ethmoid, ant.) and the foramen ethmoidale posterius (for the a. ethmoid, 

 poster.; n. ethmoid, poster., rr. orbital, gangl. sphenopalat.). The inferior surface of the pars 

 orbit., fades orbitalis, is smooth and presants near its medial anterior angle a small depression, 

 the fovea trochlearis (and occasionally laterally near it a small spur, spina trochlearis} (for 

 the trochlea m. obliqui oculi super.) ; in the lateral portion, bounded in front by the margo 

 supraorbit., lateralward by the proc. zygomat. , lies the fossa fjlandulac lacrimalis (for the 

 glandula lacrim. sup.). The upper surface, fades cerebralis, presents strong juga cerebralia 

 and impressiones digitatae. At the junction of the partes orbitales with the squama frontalis 

 the bone contains within it, the sinus frontalcs or frontal sinuses, cavities between the plates 

 of the partes orbitales and the squama of varying width and lined by mucous membrane. 

 They are subdivided by the septum sinuum frontalium, which usually diverges somewhat from 

 the median plane; the entrances lie in the anterior medial angles of the partes orbitales. 

 Spalteholz, Atlas. 2 



