Limbs vs. jaws: Can they be compared?

Abstract

Current experimental research on mammalian limb muscle structure and function is compared to that on mammalian jaw muscles. Two major areas of comparison are stressed: structural and functional. Comparisons of limbs and jaws are made from the point of view of the impact of recent studies on simple mechanical models of limb/jaw muscle function. Limb muscle structure is compared to jaw muscles at the level of muscle architecture, muscle histochemical and motor unit properties, and the organization of motor units into neuromuscular compartments. Such comparisons reveal that although limb muscles and jaw muscles might be organized in similar ways, fundamental differences exist, both in terms of muscle structure and the functional conclusions which have been based on studies of muscle structure. The comparisons also demonstrate that much recent evidence from structural studies have had little direct impact on simple models of muscle function but a much larger influence on the assumptions of the models. Comparisons of limb/jaw muscle function from kinematic and EMG studies, indicate that many masticatory strategies are used by different mammals but the basic problems of posture and locomotion have been met with essentially similar solutions, even among diverse mammalian groups. The results of such comparisons demonstrate that both limb and jaw muscle function are sufficiently complex that new or re-vitalized models are needed if the relationship between structure and function are ever to be understood. © 1985 by the American Society of Zoologists.