Doctoral Dissertation Research: Assessing the chewing function of the hyoid bone and the suprahyoid muscles in primates

The hyoid is a small u-shaped bone that sits at the base of the tongue and the top of the larynx (voice box). The shape and muscular attachments to this bone are important for tongue movements, chewing, swallowing, and vocalization. This doctoral dissertation research investigates the relationship between shape, position, and muscular attachment of the hyoid to determine the role of this bone in feeding across primates. This work informs researchers about the function of the hyoid, which may result in the formation of novel treatments for speech and swallowing disorders in humans. This work also builds STEM talent by supporting undergraduate and graduate training and creating an openly available dataset of microCT scans that can be used in scientific outreach projects aimed at K-12 students and the public. Overall, this work is poised to educate the public on scientific and evolutionary concepts, build and encourage future researchers, and add to the current understanding of head and neck anatomy and function, which has important biomedical implications. The hyoid and the muscles that connect it to the skull (i.e., the suprahyoid muscles), are central to chewing, swallowing, tongue manipulation, and vocalization. How these behaviors, specifically those involved in feeding, affect hyoid anatomy is not well known as previous work has focused on vocalization as a driving factor for hyoid shape. The hyoid is in near-constant motion during feeding and is pulled toward the oral cavity during swallowing by the suprahyoid muscles. The goal of this research is to quantify the impact of swallowing by evaluating variation in hyoid shape and position and their relationship to the suprahyoid muscles and skull in primates. This project utilizes microCT scans and iodine staining methods to visualize the hyoid apparatus along with 3D shape analyses to investigate the relationships between the hyoid, skull, and musculature. Additionally, this work analyzes how these relationships change throughout growth and development in two closely related species of primates with notable differences in diet. In doing so, this work can provide valuable insights into the evolution of human hyoid shape and function and put human hyoid anatomy into the broader context of primate hyoid variation. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.