A comparison of different physical stomach models and an analysis of shear stresses and strains in these system.

In this study, typical stomach characteristics, including the Migrating Motility Complex (MMC) and fed contractile pattern, have been summarised. The pH changes and enzyme degradation are discussed. Physical gastrointestinal models have been compared in terms of their advantages and disadvantages. The structures of the produced stomach parts are compared among the in-vitro models. Mathematical features of the models, including breaking time, emptying time and typical levels of shear stress and shear rate, have also been compared. Beaker-type systems typically involve shear stresses and strains that are orders of magnitude different from those in more realistic stomach systems. Transparent materials may help to observe the flow pattern and food breakdown in the stomach, while elastic materials may help to simulate the peristaltic movement. These models have considerable potential for answering questions about the dissolution and delivery of tablets, as well as answering fundamental questions about the hydrodynamics of the stomach and ultimately investigating diseases of the human gastrointestinal system.