96 



THE SKELETON 



The alveolar part or superior border is hollowed out into eight sockets or 

 alveoli. These are conical in shape and form an exact counterpart of the roots 

 of the teeth which thej^ contain. From the lateral aspect of the alveolar process, 

 as far forward as the first molar tooth, the buccinator muscle takes origin. 



The base or inferior border is thick and rounded. In the anterior part of its 

 extent it gives attachment to the plafysma, and near its junction with the ramus 

 is a groove for the external maxillary artery which here turns upward into the face. 



The ramus is thinner than the body and quadrilateral in shape. The lateral 

 surface is flat, gives insertion to the masseter, and at the lower part is marked by 

 several oblique ridges for the attachment of tendinous bundles in the substance 

 of the muscle. The medial surface presents near the middle the mandibular 

 (inferior dental) foramen, leading into the mandibular (inferior dental) canal 

 which traverses the bone and terminates at the mental foramen on the lateral 

 surface of the body. From the canal, which in its posterior two-thirds is nearer to 

 the medial, and in its anterior third nearer to the lateral, surface of the mandible, 



Fig. 120. — ^The Mandible. (Lateral view.) 



Coronoid 

 Temporal process 



Mandibular 



notch External 



Mental 

 foramen 

 Mentalis- 

 Quadratus- 

 labii inf. 

 The chin or. 

 mental pro- 

 tuberance 



Angle 



Platysma 

 Triangularis oris 

 External oblique line 



Groove for external maxillary artery 



a series of small channels pass upward to the sockets of the posterior teeth and 

 transmit branches of the inferior alveolar (dental) vessels and nerve; in front of 

 the mental foramen a continuation of the canal extends forward and conveys the 

 vessels and nerves to the canine and incisor teeth. The mandibular foramen is 

 bounded medially by a sharp margin forming the lingula (mandibular spine), 

 which gives attachment to the spheno-mandibular ligament. 



The posterior margin of the lingula is notched. This notch forms the 

 commencement of a groove, the mylo-hyoid groove [sulcus mylohyoideus], 

 which runs obliquely downward and forward and lodges the mylo-hyoid nerve 

 and artery, and, in the embryo, Meckel's cartilage. Behind the spine is a rough 

 area for the insertion of the internal 'pterygoid muscle. 



The posterior Ixjrder of tiie ramus is thick and rounded, and in meeting the 

 inferior border of the ramus forms the angle of the jaw, which is rough, obtuse, 

 usually everted, and about 122° in the adult; the angle gives attachment to the 

 stylo-mandibuhir ligament. The inferior border is tliick, rounded, and continu- 

 ous with the base. The anterior border is continuous with the oblique line, 

 wliilst t he upper border presents two processes separated by a deep concavity, the 

 mandibular (sigmoid) notch. Of the processes, the anterior is the coronoid; the 

 posterior, the condylar. 



