The mandible, or lower jaw, is the bone that forms the lower part of the skull, and along with the maxilla (upper jaw), forms the mouth structure. Movement of the lower jaw opens and closes the mouth and also allows for the chewing of food. The lower set of teeth in the mouth is rooted in the lower jaw.

Four different muscles connect to the lower jaw to facilitate its movement. These muscles are the masseter, the temporalis, the medial pterygoid, and the lateral pterygoid. Each of these muscles occurs in pairs, with one of each muscle appearing on either side of the skull. The muscles work in combination to pivot the lower jaw up and down and to allow movement of the jaw from side to side.

Fractures to this bone may be minor or severe, with more severe fractures requiring the jaw to be wired shut to prevent movement during healing. Other injuries and infections that can affect the lower jaw include tendinitis, infections stemming from tooth decay or other tooth injuries, and temporomandibular joint disorder (TMJD), which causes painful swelling where the mandible meets the cheekbone.