underkæben

Underkæben, or the lower jaw, is the largest and strongest bone of the human skull. In anatomy, it is known as the mandible and forms the lower jaw framework that supports the lower teeth and provides the primary mechanism for chewing. The mandible is a U-shaped bone consisting of a horizontal body and two vertical rami, meeting at the angle where the body and ramus converge.

The body contains the alveolar process that houses the lower teeth. On its medial surface runs the mandibular canal, which carries the inferior alveolar nerve and vessels; the mental foramen on the anterior aspect transmits the mental nerve and vessels to supply the chin and lower lip. Each ramus has a condylar process that articulates with the temporal bone at the temporomandibular joint, allowing hinge-like and gliding movements essential for chewing and speech. The coronoid process provides attachment for jaw muscles.

Developmentally, the mandible forms mainly by intramembranous ossification and grows in size during childhood and adolescence, reaching near-adult dimensions later in life. Functionally, it supports dental occlusion, enables mastication, and contributes to facial aesthetics and articulation. The mandible is supplied by the inferior alveolar nerve (branch of V3) and artery, and is innervated and vascularized along its internal and external surfaces.

Clinically, mandibular injuries are common after trauma and may involve fractures of the body or ramus, sometimes requiring surgical reduction and immobilization. Orthognathic procedures such as sagittal split osteotomy adjust the position of the mandible to correct bite or facial balance. Dental anesthesia often targets the inferior alveolar nerve to numb the lower teeth.