THE MANDIBLE 



173 



spines, on either side of the middle line, is an oval depression for the attachment 

 of the anterior belly of the Digastricus. Extending upward and backward on either 

 side from the lower part of the symphysis is the mylohyoid line, which gives origin 

 to the Mylohyoideus; the posterior part of this line, near the alveolar margin, 

 gives attachment to a small part of the Constrictor pharyngis superior, and to 

 the pterygomandibular raphe. Above the anterior part of this line is a smooth 

 triangular area against which the sublingual gland rests, and below the hinder 

 part, an oval fossa for the submaxillary gland. 



Borders. The superior or alveolar border, wider behind than in front, is hollowed 

 into cavities, for the reception of the teeth; these cavities are sixteen in number, 

 and vary in depth and size according to the teeth which they contain. To the 

 outer lip of the superior border, on either side, the Buccinator is attached as 

 far forward as the first molar tooth. The inferior border is rounded, longer than 

 the superior, and thicker in front than behind; at the point where it joins the 

 lower border of the ramus a shallow groove; for the external maxillary artery, 

 may be present. 



hyoideus 



Mylohyoid line 



BODY 



^^^^ FIG. 177. Mandible. Inner surface. Side view. 



\ 



The Ramus (ramus mandibulcp; perpendicular portion). The ramus is quadri- 

 lateral in shape, and has two surfaces, four borders, and two processes. 



Surfaces. The lateral surface (Fig. 176) is flat and marked by oblique ridges 

 at its lower part; it gives attachment throughout nearly the whole of its extent 

 to the Masseter. The medial surface (Fig. 177) presents about its center the oblique 

 mandibular foramen, for the entrance of the inferior alveolar vessels and nerve. 

 The margin qf this opening is irregular; it presents in front a prominent ridge, 

 surmounted by a sharp spine, the lingula mandibulse, which gives attachment to 

 the sphenomandibular ligament ; at its lower and back part is a notch from which 

 the mylohyoid groove runs obliquely downward and forward, and lodges the mylo- 

 hyoid vessels and nerve. Behind this groove is a rough surface, for the insertion 

 of the Pterygoideus internus. The mandibular canal runs obliquely downward 

 and forward in the ramus, and then horizontally forward in the body, where it 

 is placed under the alveoli and communicates with them by small openings. On 

 arriving at the incisor teeth, it turns back to communicate with the mental foramen, 

 giving off two small canals which run to the cavities containing the incisor teeth. 





