Käftpar

Käftpar is a term used in anatomy and biology to denote a paired set of jaw structures that work together to seize, cut, and process food. The word derives from the Swedish käft (jaw) and par (pair). The concept covers both vertebrate jaws and paired mouthparts found in many invertebrates, though the specific structures vary by lineage.

In vertebrates, a käftpar typically consists of an upper jaw and a lower jaw. The upper jaw, or maxilla, is usually fixed to the skull, while the lower jaw, or mandible, is movable and hinged by the temporomandibular joint. The paired arrangement enables efficient biting and chewing through coordinated motion and force distribution. In humans and other mammals, these jaws are part of a complex system that supports vocalization, food processing, and facial expression.

In invertebrates, jaw parts are part of the mouthparts and are often specialized for particular diets. Examples include paired mandibles in many insects and crustaceans, which can be adapted for cutting, grinding, piercing, or holding prey. Across groups, the pharyngeal arches or corresponding segments give rise to these paired structures during development.

Developmentally, jaw pairs arise from embryonic tissues such as pharyngeal arches in vertebrates, with contributions from neural crest cells shaping the skull and jaw bones. Functionally, käftpar enable feeding, defense, and interaction with the environment, and they have undergone extensive diversification through evolution.

See also: jaw, mandible, maxilla, gnathostome, mouthparts.