New Insights into Macaque Hyolingual Anatomy: A Preliminary microCT Study

Abstract

The macaque (Macaca mulatta) is a promising model organism for the integrated study of the neurological and biomechanical basis of human feeding disorders. However, while feeding behavior has been extensively studied in the macaque, we have limited knowledge about its three‐dimensional hyolingual myoarchitecture, especially of the intrinsic musculature of the tongue. This preliminary study reports the results of a digital dissection utilizing radiopaque staining techniques and micro‐computed tomography. A 1:1 solution of 5% Lugols and 190 proof ethanol increased muscle contrast in the isolated hyolingual apparatus of a female Rhesus macaque, permitting segmentation of these tissues to resolve their three‐dimensional morphology. The scans showed that the macaque hyolingual apparatus shares many similarities with that of humans, excepting well‐known differences such as a more cranial hyoid resulting in a flatter tongue. However, the posterior third of the tongue has significantly higher levels of connective tissue relative to the anterior two‐thirds of the tongue. Given the importance of the posterior tongue in the “squeeze back” mechanism of swallowing seen in macaques and humans, such architecture may have important functional implications during feeding. Future directions include utilizing similar methods for comparative study among other mammals (including humans), marker‐based study of three‐dimensional soft tissue kinematics, and development of a computational model for feeding behaviors.