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.

Simulation studies of the role of esophageal mucosa in bolus transport

“…We conducted simulations based on a fully resolved computational model of esophageal transport (Kou et al 2015a). The model integrates three essential aspects (liquid-like bolus, esophageal wall, and muscle activation) into a single simulation and is therefore capable of fully resolving interactions among the three.…”

“…The model integrates three essential aspects (liquid-like bolus, esophageal wall, and muscle activation) into a single simulation and is therefore capable of fully resolving interactions among the three. The model has been validated (Kou et al 2015a) and used to study the role of muscle activation in esophageal transport (Kou et al 2015b). Hence, we provide here only a brief discussion on our computational model and refer to our previous work (Kou et al 2015a) for details.…”

“…The active and passive properties of the muscular layers have been relatively well studied (Nicosia and Brasseur 2002; Jung et al 2004; Ghosh et al 2005; Mittal et al 2006; Brasseur et al 2007; Zhao et al 2007; Kou et al 2015a). However, the submucosa and mucosa, here collectively called mucosa, has been the object of relatively little research relating to bolus transport.…”

A multiphase flow in the antroduodenum: some results of the mathematical modelling and computational simulation

“…CFD (Computation Fluid Dynamics) models meet these purposes, allowing to assess and predict flow characteristics at any point of simulation domain. Nowadays models of fluid flow in the esophagus [12,13], stomach [14,15] and bowel [16][17][18] are developing rapidly. Available models of the stomach or duodenum mainly account for the peristaltic waves in the antrum [19,20] and gut [21].…”

Numerical modeling of acidity distribution in antroduodenum aimed at identifying anomalous zones at consuming drinks with different pH level

“…Mathematical models used for describing food flow in esophagus, [7,25], stomach [14,15,18], and bowels [17,16,19], have been actively developed over the last decade. We should note that researchers, when developing models, as a rule consider tract motor function while biochemical reactions, digestive glands secretions, and food components absorption are given less attention.…”