Flow and mixing induced by single, colinear, and colliding contractile waves in the intestine

Abstract

Smooth muscle-lined organs like the gut, the ureter, and the fallopian tubes transport matter by generating traveling contractile waves. Intestinal peristalsis is characterized by rhythmic trains of shallow, low-amplitude myogenic waves and high-amplitude, lumenobliterating neurogenic waves. In this paper, we develop a simple analytical Poiseuille-flow model to predict the flow rates induced by these different contractions as a function of all relevant wave parameters, and compare them to a numerical fluid-solid finite element model. We rationalize experimentally observed bolus to-and-fro motion induced by shallow myogenic waves. We show that occluding waves induce considerable bolus mixing due to an upstream vortex. We then investigate the hydrodynamics induced by two waves propagating either in the same direction (colinear) or in opposite directions, as happens in the digestive tract. For colinear waves, we find that the bolus reflux is maximal at a distance between successive myogenic waves close to the one observed physiologically. Colliding waves create a high pressure region that gives rise to rapid fluid flow, high shear stress, and radial mixing upon annihilation. Our paper provides fundamental insight on the fluid dynamics (reflux, propulsion, and mixing) generated by different contraction patterns of the intestine.

Optimal free-surface pumping by an undulating carpet

“…c The rescaled experimental data of Fig. 3b are in excellent agreement with the theoretical prediction of (7), plotted as the solid black line. Error bars are based on standard deviation.…”

“…The necessity to manipulate flow and transport liquids is primitive to many biophysical processes such as embryonic growth and development 1,2 , mucus transport in bronchial tree [3][4][5] , the motion of food within intestine 6,7 , animal drinking 8,9 . Engineered systems also rely on efficient liquid transport such as in heat sinks and exchangers for integrated circuits 10,11 , micropumps 12,13 , and lab-on-a-chip devices 14 .…”

Peristaltic transport of a power-law fluid induced by a single wave: A numerical analysis using the cumulant lattice Boltzmann method

“…The contraction ratio may vary over a wide range in physiological conditions. Agbesi and Chevalier, 11 for example, observed D p =D $ 0.12-0.88 in their animal experiments. Figure 3…”

“…Analytical solutions are also valid for infinitely long wavelengths, but some contraction waves have wavelengths similar to or shorter than the diameter of the intestine. Agbesi and Chevalier, 11 for example, reported short wavelengths of k=D $ 0.5-1.5 in the mice hindgut and chicken embryonic midgut.…”

“…[13][14][15] Peristaltic transport by an isolated contraction wave has also been studied. 8,11,16 In addition, some studies focused on the dynamics of particles in peristaltic flows. [17][18][19] However, the peristaltic flow of power-law fluids with low-behavior indices is not fully understood.…”