Henry Gray (18251861). Anatomy of the Human Body. 1918.
Articulations.The vomer articulates with six bones: two of the cranium, the sphenoid and ethmoid; and four of the face, the two maxillæ and the two palatine bones; it also articulates with the septal cartilage of the nose.
5b. 8. The Mandible (Lower Jaw)
(Inferior Maxillary Bone)
The mandible, the largest and strongest bone of the face, serves for the reception of the lower teeth. It consists of a curved, horizontal portion, the body, and two perpendicular portions, the rami, which unite with the ends of the body nearly at right angles.
The Body (corpus mandibulæ).The body is curved somewhat like a horseshoe and has two surfaces and two borders.
Surfaces.The external surface(Fig. 176) is marked in the median line by a faint ridge, indicating the symphysis or line of junction of the two pieces of which the bone is composed at an early period of life. This ridge divides below and encloses a triangular eminence, the mental protuberance, the base of which is depressed in the center but raised on either side to form the mental tubercle. On either side of the symphysis, just below the incisor teeth, is a depression, the incisive fossa, which gives origin to the Mentalis and a small portion of the Orbicularis oris. Below the second premolar tooth, on either side, midway between the upper and lower borders of the body, is the mental foramen, for the passage of the mental vessels and nerve. Running backward and upward from each mental tubercle is a faint ridge, the oblique line, which is continuous with the anterior border of the ramus; it affords attachment to the Quadratus labii inferioris and Triangularis; the Platysma is attached below it.
The internal surface(Fig. 177) is concave from side to side. Near the lower part of the symphysis is a pair of laterally placed spines, termed the mental spines, which give origin to the Genioglossi. Immediately below these is a second pair of spines, or more frequently a median ridge or impression, for the origin of the Geniohyoidei. In some cases the mental spines are fused to form a single eminence, in others they are absent and their position is indicated merely by an irregularity of the surface. Above the mental spines a median foramen and furrow are sometimes seen; they mark the line of union of the halves of the bone. Below the mental