|Figure 1: Mandible. Outer surface. Side view|
|Figure 2: Mandible. Inner surface. Side view|
|Gray's||subject #44 172|
|Precursor||1st branchial arch|
The mandible (from Latin mandibŭla, "jawbone") or inferior maxillary bone is, together with the maxilla, the largest and strongest bone of the face. It forms the lower jaw and holds the lower teeth in place. The mandible 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.
('corpus mandibulæ') The body is curved somewhat like a horseshoe and has two surfaces and two borders.
The external surface [Fig. 1] 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.
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 depressor labii Inferioris (Quadratus labii inferioris) and depressor anguli oris (Triangularis); the platysma is attached below it.
The internal surface [Fig. 2] 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 genioglossus.
Immediately below these is a second pair of spines, or more frequently a median ridge or impression, for the origin of the geniohyoid.
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 spines, on either side of the middle line, is an oval depression for the attachment of the anterior belly of the digastric.
Extending upward and backward on either side from the lower part of the symphysis is the mylohyoid line, which gives origin to the mylohyoid; 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 raphé.
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 facial artery, may be present.
- See Ramus mandibulae
The mandible articulates with the two temporal bones at the temporomandibular joints.
Mandibular fractures are often accompanied by a 'twin fracture' on the contralateral (opposite) side.
The mandible may be dislocated anteriorly (to the front) and inferiorly (downwards) but very rarely posteriorly (backwards).
- Bone terminology
- Terms for anatomical location
- Changes produced in the mandible by age
- Ossification of the mandible