The flow through the pharynx from the GPJ to the UES has been numerically investigated with a non-Newtonian fluid obeying the power law with similar rheological indices to a contrast medium used in videofluroscopy. Flow fields revealed the occurrence of reflux regions in the beginning, being this effect stronger at low entrance pressure, which could be related to abnormal swallowing. As a consequence, the bolus travels preferably along the walls. It has been also observed that the bolus head travels faster than the bolus tail, which indicates that the bolus is elongated. Results from this work can be further used for a rheological characterization of oral nutritional supplements for patients suffering from swallowing disorders. PRACTICAL APPLICATIONSThe flow through the pharynx has been numerically investigated with a non-Newtonian fluid to get insight about causes leading to abnormal swallowing. Reflux has been observed in the beginning as result of a central stream and two symmetric loops generated along the walls, being this effect at low peristaltic pressure. Velocity fields revealed that the bolus head travels faster than the bolus tail, which is a result of the geometry and conservation of mass. Under these conditions, extensional stresses are generated by the flexion of the pharynx walls. Shear rate fields allowed establishing the shear rate range at which the bolus is subjected along the pharynx, which is useful for the rheological characterization of supplements for patients suffering from swallowing disorders. presses against the hard palate and the bolus is finally propelled to the GPJ. Under normal conditions, both the nasopharynx and the larynx are occluded, and during this phase, chewing, breathing and other activities are inhibited. From the GPJ to the UES, the bolus goes over a distance of 5 cm in about 1 s. During that period, some protective mechanisms, such as the closure of vocal fold, prevents aspiration during deglutition (Leder et al. 2013). The bolus moves down toward the esophagus and the passage through it is carried out at a rate of 2.5 to 5 cm/s. However, a very bs_bs_banner A journal to advance the fundamental understanding of food texture and sensory perception Journal of Texture Studies

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We aimed to provide realistic three-dimensional (3D) models to be used in numerical simulations of peristaltic flow in patients exhibiting difficulty in swallowing, also known as dysphagia. To this end, a 3D model of the upper gastrointestinal tract was built from the color cryosection images of the Visible Human Project dataset. Regional color heterogeneities were corrected by centering local histograms of the image difference between slices. A voxel-based model was generated by stacking contours from the color images. A triangle mesh was built, smoothed and simplified. Visualization tools were developed for browsing the model at different stages and for virtual endoscopy navigation. As result, a computer model of the esophagus and the stomach was obtained, mainly for modeling swallowing disorders. A central-axis curve was also obtained for virtual navigation and to replicate conditions relevant to swallowing disorders modeling. We show renderings of the model and discuss its use for simulating swallowing as a function of bolus rheological properties. The information obtained from simulation studies with our model could be useful for physicians in selecting the correct nutritional emulsions for patients with dysphagia.

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