LATERAL REGION OF THE SKULL. 



183 



LATEEAL BEGION OF THE SKULL. 



The Lateral Eegion of the Skull is of a somewhat triangular form, the base 

 of the triangle being formed by a line extending from the external angular 

 process of the frontal bone along the temporal ridge backwards to the outer 

 extremity of the superior curved line of the occiput : and the sides by two 

 lines, the one drawn downwards and backwards from the external angular pro- 

 cess of the frontal bone to the angle of the lower jaw, the other from the angle 

 of the jaw upwards and backwards to the extremity of the superior curved 

 line. This region is divisible into three portions, temporal, mastoid, and 

 zygomatic. 



The Temporal Fossa is bounded above and behind by the temporal ridge, 

 which extends from the external angular process of the frontal upwards and 

 backwards across the frontal and parietal bones, curving downwards behind to 

 terminate at the root of the zygomatic process. In front, it is bounded by the 

 frontal, malar, and great wing of the sphenoid : externally, by the zygomatic 

 arch, formed conjointly by the malar and temporal bones ; below it is separated 

 from the zygomatic fossa by the pterygoid ridge, seen on the outer surface of 

 the great wing of the sphenoid. This fossa is formed by five bones, part of 



Fig. 131. Side Yiew of the Skull. 



the frontal, great wing of the sphenoid, parietal, squamous portion of the 

 temporal and malar bones, and is traversed by five sutures, the transverse facial, 

 coronal, spheno-parietal, squamo-parietal, and squamo-sphenoidal. It is deeply 

 concave in front, convex behind, traversed by grooves which lodge branches 

 of the deep temporal arteries, and filled by the Temporal muscle. 



