title: A fully resolved active musculo-mechanical model for esophageal transport.
abstract: Esophageal transport is a physiological process that mechanically transports an ingested food bolus from the pharynx to the stomach via the esophagus, a multilayered muscular tube. This process involves interactions between the bolus, the esophagus, and the neurally coordinated activation of the esophageal muscles. In this work, we use an immersed boundary (IB) approach to simulate peristaltic transport in the esophagus. The bolus is treated as a viscous fluid that is actively transported by the muscular esophagus, and the esophagus is modeled as an actively contracting, fiber-reinforced tube. Before considering the full model of the esophagus, however, we first consider a standard benchmark problem of flow past a cylinder. Next a simplified version of our model is verified by comparison to an analytic solution to the tube dilation problem. Finally, three different complex models of the multi-layered esophagus, which differ in their activation patterns and the layouts of the mucosal layers, are extensively tested. To our knowledge, these simulations are the first of their kind to incorporate the bolus, the multi-layered esophagus tube, and muscle activation into an integrated model. Consistent with experimental observations, our simulations capture the pressure peak generated by the muscle activation pulse that travels along the bolus tail. These fully resolved simulations provide new insights into roles of the mucosal layers during bolus transport. In addition, the information on pressure and the kinematics of the esophageal wall resulting from the coordination of muscle activation is provided, which may help relate clinical data from manometry and ultrasound images to the underlying esophageal motor function.
authors.affiliation: Theoretical and Applied Mechanics, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA.
authors.forename: Wenjun
authors.initials: W
authors.lastname: Kou
authors.affiliation: Department of Mechanical Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA.
authors.forename: Amneet Pal Singh
authors.initials: AP
authors.lastname: Bhalla
authors.affiliation: Department of Mathematics, University of North Carolina at Chapel Hill, Phillips Hall, Campus Box 3250, Chapel Hill, North Carolina 27599-3250, USA.
authors.forename: Boyce E
authors.initials: BE
authors.lastname: Griffith
authors.affiliation: Department of Medicine, Feinberg School of Medicine, Northwestern University, 676 North Saint Clair Street, 14th Floor, Chicago, Illinois 60611, USA.
authors.forename: John E
authors.initials: JE
authors.lastname: Pandolfino
authors.affiliation: Department of Medicine, Feinberg School of Medicine, Northwestern University, 676 North Saint Clair Street, 14th Floor, Chicago, Illinois 60611, USA.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Kahrilas
authors.affiliation: Department of Mechanical Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA.
authors.forename: Neelesh A
authors.initials: NA
authors.lastname: Patankar
keywords: esophageal transport; fluid-structure interaction; immersed boundary method; muscle activation