Functional Morphology of Mammalian Mastication

SYNOPSIS. While chewing is not unique to mammals, it is oneof their most distinctive characteristics. Historically, studiesof food processing in mammals were intended to provide evolutionaryinsights, but more progress has been made in understanding mechanisticaspects. Mastication is considered under five headings. (1)Interaction of teeth with food.Knowledge of comparative dentalanatomy and function is advanced in comparison to understandingof foods and how they are broken down. (2) Chewing force andits resistance by the skull. The traditional assumption thatocclusal force is maximized is not always justified, and experimentalresults suggest that skull loading is far more dynamic and variablethan had been envisioned from theoretical analyses. (3) Howthe jaw moves. The most important masticatory movement is thatof the power stroke, and in most but not all species this isinfluenced more by the inclined planes of the teeth and jawjoints than by the musculature. (4) The role of muscles in producingboth force and movement. The most fundamental distinction amongjaw muscles is whether they have a rostral or caudal directionof pull, as this determines their role in transverse jaw movements.Reliance on anatomical names tends to obscure functional similaritiesand differences among species. (5) Intraoral structures. Becausethey are difficult to study, the actions of the tongue and pharynxare still debated. Even the fundamental question of whethermammals can breathe and swallow at the same time has not beendefinitively answered.