252 



Anatomy of Skeleton 



The upper border forms a thick orbital margin at its junction with the orbital surface, 

 and this margin is prolonged inwards on to the infraorbital process, making more 

 than half of the lower margin of the orbit ; it is prolonged up to meet the frontal bone 

 at the frontal process. The front margin has already been noticed as articular : the 

 lower or masseteric border is rounded and leads back.to the zygomatic or temporal process, 

 which joins the zygoma by a rough surface, bevelled internally and directed obliquely 

 upwards and forwards ; above this the posterior border gives attachment to the tem- 

 poral fascia, and a strong band of this fascia is fastened to a prominent marginal or 

 malar tubercle near the top (a in Fig. 200) of this border below the frontal process. 



The temporal surface is the upper and outer part of the angle included between 

 the two constituent plates of the bone, the lower and inner part being articular for the 

 maxilla : the temporal surface is therefore deeply concave, with a front wall made by 

 the orbital plate and a back or outer watt formed by the upper part of the facial plate, 



frontal 

 process. 



F. 



F. 



n. 



FIG. 200. Left malar bone. Left figure, from the front : central figure, orbital aspect ; right 

 figure, posterior aspect. Articulating areas : F, with frontal ; M. with maxilla ; S. with 

 sphenoid ; T. with temporal ; a. malar tubercle ; b. orbital margin ; c. facial surface covered 

 by Orbicularis ; d. orbital surface ; e. temporal surface ; g. origin of Temporal muscle ; 

 h. origin of Masseter ; X. non-articular border forming outer end of sphenomaxillary fissure ; 

 /. tubercle for attachment of " check ligament " of Rectus externus. 



and below and behind this by the inner surface of the zygomatic portion of this plate. 

 The surface aids in the formation of the temporal fossa : the Temporal muscle arises 

 from the upper part of its front wall ; below this it is in relation with the muscle and 

 a movable pad of fat, and here the temporal division of the temporo-malar nerve 

 has its exit and lies between the bone and the muscle : the lower and back part of 

 this surface is in contact with Temporal muscle, and its lower portion gives origin 

 to the front fibres of Masseter : this muscle arises only from the deep aspect of the 

 zygomatic part and from the lower margin, not at all from the outer surface. 



The malar canals or foramina vary in number ; there may be a common opening 

 for the temporo-malar nerve with a double exit, or the nerve may enter the bone in 

 two divisions, thus making four openings instead of three. 



Development. 



A bony centre appears in membrane outside and below the level of the eye at 

 the end of the second month, and from this the ossification extends upwards and 

 inwards, forwards and backwards. It is doubtful whether other centres are normally 



