underkäken

Underkäken, in Swedish anatomy, refers to the mandible or lower jaw, the largest and strongest bone of the skull. It forms the lower framework of the face, houses the lower dentition, and plays a central role in mastication, speech, and facial expression. In the adult, the mandible is a single U-shaped bone that typically consists of a horizontal body (corpus) and two upright rami. The body bears the lower teeth on its occlusal surface, while each ramus extends upward to contact the temporal bone at the temporomandibular joint (TMJ). At the upper end of each ramus are the condylar process (which contains the mandibular condyle) and the coronoid process, separated by the mandibular notch.

The mandible articulates with the skull at the temporomandibular joints, which are synovial joints allowing hinge and gliding movements essential for chewing. Developmentally, the mandible forms by intramembranous ossification and fuses at the mandibular symphysis during early adulthood.

Nerve supply comes primarily from the inferior alveolar nerve, a branch of the mandibular division of the trigeminal nerve, which enters via the mandibular foramen and provides sensation to the lower teeth; the mental nerve supplies the chin and lower lip. Blood supply is mainly from the inferior alveolar artery, with drainage via the pterygoid venous plexus.

Clinical relevance includes mandible fractures, dental malocclusion, temporomandibular joint disorders, and reconstructive surgery following trauma or disease. The mandible's unique mobility and central role in mastication make it a key component of craniofacial anatomy.