Your jawbone is the only bone in the skull you can actually move
Leave aside the tiny vibrating bones of the middle ear, and the mandible is the one part of the human skull that moves at will. It swings open and shut, slides sideways and pushes forward, and since farming began about 10,000 BCE human jaws have been shrinking.
The name comes from the Latin mandibula, roughly 'for chewing'. In humans it is the largest and lowest bone of the face and the strongest in the facial skeleton, linked to the skull's temporal bones by the temporomandibular joints on each side. Those joints allow more than a hinge action, which is why people can grind food from side to side and jut the chin forward.
Its shape is a horseshoe-curved body with two upright branches, the rami, rising at the back to form the nearly square angle of the jaw. A faint ridge down the middle of the chin marks the symphysis, where two halves joined, and below it the chin itself bulges as a triangular mound. The upper edge of the body is carved into 16 sockets for the lower teeth. At the top of each ramus sit two projections: the thin, triangular coronoid in front and the thicker condyle behind, which forms part of the jaw joint, separated by a deep crescent-shaped notch.
Muscles crowd onto it. The powerful masseter covers almost the whole outer face of each ramus, the medial pterygoid grips the inside of the angle, the buccinator runs along the outer edge of the tooth row as far as the first molar, and the genioglossus, which pulls the tongue, anchors to small spines behind the chin. Two openings on each side carry nerves: the mandibular foramen in the middle of the ramus and the mental foramen near the chin, usually below the premolars.
Through them runs the inferior alveolar nerve, a branch of the trigeminal system that gives feeling to the lower gums and teeth before splitting into incisive and mental branches, the latter emerging near the chin. With age the bone tends to change shape, and it can fracture. Surgeons can remove fragments or even the entire bone and use regenerative techniques, and the jaw carries considerable weight in forensic identification.
Source: Mandible
