Imaging and modelling of digestion in the stomach and the duodenum

Abstract

Gastroduodenal physiology is traditionally understood in terms of motor-secretory functions and their electrical, neural and hormonal controls. In contrast, the fluid-mechanical functions that retain and disperse particles, expose substrate to enzymes, or replenish the epithelial boundary with nutrients are little studied. Current ultrasound and magnetic resonance imaging allows to visualize processes critical to digestion like mixing, dilution, swelling, dispersion and elution. Methodological advances in fluid mechanics allow to numerically analyse the forces promoting digestion. Pressure and flow fields, the shear stresses dispersing particles or the effectiveness of bolus mixing can be computed using information on boundary movements and on the luminal contents. These technological advances promise many additional insights into the mechanical processes that promote digestion and absorption.

Bedside ultrasound assessment of gastric content: an observational study

“…Ultrasound has been used to evaluate gastric wall lesions 19,20 and changes in gastric volume during accommodation and emptying of the stomach. 21,22 Sequential sonographic evaluation of the gastric antrum can be used to study time for gastric emptying, and it correlates well with scintigraphic evaluation, the current gold standard. [23][24][25][26][27] In anesthesiology and acute care medicine, there is a growing interest in bedside evaluation of gastric ''fullness'' to assess pulmonary aspiration risk.…”

Technologies and Analyses Using Medaka to Evaluate Effects of Space on Health

“…Even though observation of internal organs has been difficult, they have been analyzed by ultrasonography or contrast medium because of the importance of their functions (Rhodes et al, 1966;Schulze, 2006;Haruma et al, 2008). Thus, we are trying to evaluate the heartbeat, peristaltic movement, or enzymatic activities of metabolism using transparent medaka with live imaging (Fig.…”

Mechanics of flow and mixing at antroduodenal junction

“…At this point, antral contraction waves approach the pyloric orifice and, along with the sphincter complex and mucosal folds, cause steady constriction of the pyloric lumen. Chyme continues to be forcibly transported through this lumen until it is fully occluded, a process thought to potentiate an effluent jet into the superior duodenum [1][2][3] . To date, it seems that no specific attention has been paid to how the geometry and contractile activity of the pylorus might impact gastric outflow and mixing in the first part of the duodenum, although mixing of chyme with duodenal contents (in particular pancreaticobiliary secretions) is essential for digestion and absorption to proceed [3] .…”

“…Following ingestion of meals, the stomach secretes gastric juice containing protein-denaturing hydrochloric acid and pepsinogen, and effectively grinds the mixture with a series of strong muscular contractions to produce a slurry of small solid particles and gastric juice known as chyme. Peristaltic contractions in the sinus of the stomach then serve to transport chyme distally into the small intestine, where further enzymatic catalysis, transport, and digestion continue [1][2][3][4] . The objective of this study is to determine what role, if any, the morphology of the antroduodenal junction ( Figure 1) plays in affecting transport and dynamic mixing of nutrients in the proximal duodenum.…”

“…The gastric outlet to the small intestine or antroduodenal junction is thought to influence the effectiveness of mixing and subsequent absorption of nutrients in the gastrointestinal tract [1][2][3] . Following ingestion of meals, the stomach secretes gastric juice containing protein-denaturing hydrochloric acid and pepsinogen, and effectively grinds the mixture with a series of strong muscular contractions to produce a slurry of small solid particles and gastric juice known as chyme.…”