Muscle · Jaw

Digastric

Musculus digastricus

A two-bellied muscle slung under the jaw like a hammock: one belly runs forward from behind the ear to a tendon anchored on the hyoid bone in the throat, and the other runs on from there to the underside of the chin. It opens the jaw when the hyoid is held down, and lifts the hyoid when you swallow. It matters because it physically links the jaw to the neck — when the head sits forward and the jaw is habitually clenched, this is one of the muscles caught between the two, and it is a common source of tenderness under the chin and behind the angle of the jaw in people whose jaw and neck complaints arrive together.