Biomechanics of the Small Intestinal Contractions

Abstract

The small intestine is a part of the gastrointestinal segment comprising of the duodenum, jejunum, and ileum. They help to process the gastric contents for further digestion, which involves mixing with duodeno-biliary-pancreatic (DBP) secretions to facilitate the chemical digestion, and homogenization of the luminal contents through contractions of the circular and longitudinal smooth muscle fibers of the intestine. The contractions of these smooth muscle fibers develops the mechanical forces at the mucosal wall, which as a consequence, transfers its momentum to the underlying fluid to develop the fluid flows, suggesting relevance of mechanics in physiology. The resulting flows are what drive the digestion. Changes in contractility of wave shapes of circular and longitudinal smooth muscle contractions and fluid rheology are known to affect the digestive process through generation of various flow patterns that differ in luminal pressure, peak velocity, extent of shearing/ mixing, volume of mixing, and flow rate. Recent studies indicate that the digestive process can be very specific such as to cause lipid digestion through segmental contractions and transport by eliciting propagating contractions, suggesting that the intestine manages to digest a variety of food in an efficient manner by eliciting appropriate contractions.

Structural breakdown of starch‐based foods during gastric digestion and its link to glycemic response: In vivo and in vitro considerations

“…The small intestine is divided into several functional regions with decreasing wall (muscle layer) thickness as they move further from the stomach: the duodenum (the first 25 cm), jejunum (around 40% of the small intestine), and ileum (around 60% of the small intestine). The inner wall of the organ (the mucosa) is covered by numerous microscopic finger‐like structures called villi with decreasing number and size at further distances from the duodenum (Avvari, 2019; Feher, 2017a; Smith & Morton et al., 2010c). The duodenum serves as the location of mixing between the chyme emptied from the stomach with secretions from the intestine, pancreas, and liver.…”

“…The resulting monosaccharides and water are absorbed in the jejunum. The ileum absorbs vitamin B 12 and bile salts, leaving residual materials to be propelled to the large intestine for fermentation (Avvari, 2019; Smith & Morton, 2010c).…”

“…Segmentation occurs more frequently in the duodenum than in other small intestinal regions (Reinke et al., 1967; Rosenbaum et al., 1967). Segmentation is responsible for mixing the secretions with the chyme received from the stomach, homogenizing the intestinal content, aiding in pH regulation in the duodenum, and facilitating contact between food particles and the intestinal mucosa for absorption (Avvari, 2019; Smith & Morton, 2010c).…”

A novel two-indenter based micro-pump for lab-on-a-chip application: modeling and characterizing flows for a non-Newtonian fluid

“…In other words, diaphragm acts as a source of mechanical forces to induce peristalsis in the channel through generation of pressure forces. Peristaltic transport in biological systems is generated by a progressive wave of contraction/expansion of the wall musculature which helps in mixing and transferring the contents to the lower parts of the tube [23–25]. Due to challenges in replicating such systems in laboratory, micro fluidic systems comprising of a number of pumping stages have been employed for developing such peristalsis like motion in engineering applications.…”

Changing flows balance nutrient absorption and bacterial growth along the gut

“…1A). While motility driven flow [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40], peristalsis-induced nutrient absorption, [41][42][43] and bacterial growth [17] have been independently investigated, the complex dynamics arising due to different motility patterns and feedback from bacteria or nutrient density remains unknown.…”