Primate Swallowing Is Powered by Both Rotation and Contraction of Suprahyoid Muscles

Morphology, function, and coordination of suprahyoid and lingual muscles are especially important determinants of swallowing performance in macaques, and probably humans. Here, we characterize suprahyoid muscle biomechanics within a dynamic framework of architectural gear ratios and pulley systems that optimize hyoid elevation velocity to quickly "prime the pump" and subsequent hyoid protraction power and/or force to drive the hydraulic mechanism of tongue base retraction. Because of muscle rotation, primate hyolingual muscle function is particularly dependent on hyoid posture and muscle geometry, which may have important implications for the evolution of swallowing biomechanics in human evolution.