Regional Tongue Anatomy and Corresponding Kinematics During Chewing and Drinking in the Pig

Abstract

Chewing and drinking are fundamental oral behaviors for nutrient ingestion in mammals. They consist of coordinated tongue and jaw movements to ingest, transport, and swallow. However, differences in bolus properties and intraoral management suggest the potential for differences in the movements and deformations performed by the tongue throughout the cycle. Additionally, regional heterogeneity of muscle fascicle orientation is observed throughout the body of the tongue which likely imposes different constraints on the capabilities of different regions to move and deform. The goal of this study is to determine how regional differences in tongue movements and deformations during chewing and drinking in pigs relate to their corresponding muscle fascicle anatomy. Muscle fascicle orientations were quantified using diffusible iodine contrast‐enhanced computed tomography (diceCT) scans relative to the sagittal plane. Cycle parameters and corresponding regional tongue deformations were analyzed during chewing and drinking using X‐ray Reconstruction of Moving Morphology (XROMM) with additional markers implanted in the soft tissues of the tongue (Ohio University Institutional Animal Care and Use Committee: protocol #12‐U‐009). Examination of muscle fascicles highlights clear regional differences in their orientations. XROMM results demonstrate differences in kinematic parameters between chewing and drinking cycles, with drinking cycles exhibiting a smaller amount of jaw movement for all degrees of freedom used during both behaviors: Tx (condylar protraction‐retraction), Rz (jaw pitch), and Ry (jaw yaw). Tongue protraction‐retraction was greater during chewing than drinking. Additionally, during both behaviors, a near‐constant total tongue length was observed, but regional contributions to total tongue length varied significantly between behaviors, with higher magnitudes of length deformations observed during chewing. This work demonstrates that different regions of the tongue do move and deform in different ways, and that they vary between chewing and drinking behaviors. The observed deformations also correspond to the underlying muscle fascicle anatomy as revealed by diceCT.