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Mandible

Other Terms: Jaw bone, Lower jaw bone, Mandibulla, Mandibula, Mandibule

Type

irregular

Description

This is the largest of the facial bones. It actually is two bones, this is still the case in most mammals, which have fused at the anterior midline and have become a single bone in humans. It has an anteriorly arched horizontal body with two vertically oriented rami projecting from the posterior aspect. The mandible is a strong bone composed predominantly of compact bone. It houses the lower tooth row in its dental arch. The strong masticatory muscles act on this bone moving it in the temporomandibular joint. Its shape can vary exceedingly with age. If the teeth are lost, bone gets resorbed on the alveolar surface leading to the thinning of the dental arch.

Etymology

This word originally arose from the Latin verb mandere meaning to chew. The bone specialized for this purpose was named the mandibulum or jaw.

Articulations

The mandible articulates with two bones: the right and left temporal bones. The condylar process of the mandibular ramus is seated in the mandibular fossa of the temporal bone where an articular disc separates the bone surfaces.

Ossification

Meckel's cartilages are the cartilaginous precursors of the mandible. These cartilaginous bars of the first branchial arch become surrounded with a fibrous membrane. These membranous covered cartilage bars are attached to the otic or ear capsules at their proximal end and to each other via mesodermal tissue at their distal extremities. The only portion of Meckel's cartilage that contributes to the mandible is the distal end. This end, invaded by bone, contributes to the part of the mandible between the two canine teeth. The major portion of the mandible forms intramembranously in the membrane surrounding Meckel's cartilage. During the sixth week of embryonic life a center arises near what will be the mental foramen. By the tenth week the anterior portion of the cartilage is invaded by the developing bone. The bone continues to spread posteriorly and superiorly to form the mandibular outline. At birth the bone is in two halves, separated by a fibrous symphysis at the anterior midline. The two halves usually ossify into one during the first year. At birth the bone is cavitated and weak forming a horizontal body with no evident ramus. By the eighth year the mandible develops a prominent ramus with a more vertical orientation. Development continues, making the ramus almost vertical in the adult mandible.

Latin

Mandibula

French

Mandibule

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