Effect of local longitudinal shortening on the transport of luminal contents through small intestine

Avvari, Ravi Kant

doi:10.1007/s10409-018-0809-5

Cited by 16 publications

(12 citation statements)

References 18 publications

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“…Flow details of the intestinal peristalsis have been recently reported in the literature [56]. When a wave of contraction propagates along the intestinal wall, they develop peripheral forces that can be directed radially inward, axially oriented, Figure 5.…”

Section: Effect Of Advancing Lls On Flowsmentioning

confidence: 94%

“…Using imaginary tracers, the author was able to determine particle trajectories due to the peristalsis-CC and LLS [56]. Two kinds of flows were observed; one resulting in axial displacement of the fluid and other causing circulation of the fluids (eddies).…”

Section: Physiological Relevance Of Intestinal Motility 61 Mixingmentioning

confidence: 99%

“…When contraction traverses at 50% occlusion, there is a higher tendency for the particles to undergo circulation; favoring mixing [56]. However, at 80% occlusion, the particles tend to under more of axial displacement and less of a radial displacement with no circulation; favoring transport.…”

Section: Transportmentioning

confidence: 99%

“…By estimating the flow resistance, the author was able to assess the importance of the slowing down of the fluid flow and increase in the retention time of the fluid near the mucosa; providing more time to undergo chemical digestion and absorption [56]. The extent of friction offered by the intestine to fluid of different flow behavior index (n = 0.6, 1.0, and 1.4) suggests that the friction is highest for pseudo-plastics and decreases with increase in flow behavior index [56]. In addition to this, friction is found to be dependent on pressure gradient; showing increasing trend with increase in pressure.…”

Section: Frictional Advantagementioning

confidence: 99%

“…Studies indicate that the intestine utilizes the LLS at its advantage to perform forceful contractions; with peak LLS not exceeding 65% [18,52]. The optimal choice of wavelength at which the shearing attains its maximum value is equal to the intestinal diameter (1 unit); higher wavelength (1.5 units) is inefficient [56]. Similarly occlusive contractions show two functions-mixing at lower occlusion and transport at higher occlusion.…”

Section: What Is the Optimal Parameter Space For Contractility?mentioning

confidence: 99%

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Biomechanics of the Small Intestinal Contractions

Avvari¹

2020

Digestive System - Recent Advances

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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.

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Section: Effect Of Advancing Lls On Flowsmentioning

confidence: 94%

Section: Physiological Relevance Of Intestinal Motility 61 Mixingmentioning

confidence: 99%

Section: Transportmentioning

confidence: 99%

Section: Frictional Advantagementioning

confidence: 99%

Section: What Is the Optimal Parameter Space For Contractility?mentioning

confidence: 99%

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Biomechanics of the Small Intestinal Contractions

Avvari¹

2020

Digestive System - Recent Advances

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Biomechanical characterization of the small intestine to simulate gastrointestinal tract chyme propulsion

Carvalho

Ferreira

Oliveira

et al. 2022

Numer Methods Biomed Eng

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Regular intestinal motility is essential to guarantee complete digestive function. The coordinative action and integrity of the smooth muscle layers in the small intestine's wall are critical for mixing and propelling the luminal content. However, some patients present gastrointestinal limitations which may negatively impact the normal motility of the intestine. These patients have altered mechanical and muscle properties that likely impact chyme propulsion and may pose a daily scenario for long‐term complications. To better understand how mechanics affect chyme propulsion, the propulsive capability of the small intestine was examined during a peristaltic wave along the distal direction of the tract. It was assumed that such a wave works as an activation signal, inducing peristaltic contractions in a transversely isotropic hyperelastic model. In this work, the effect on the propulsion mechanics, from an impairment on the muscle contractile ability, typical from patients with systemic sclerosis, and the presence of sores resultant from ulcers was evaluated. The passive properties of the constitutive model were obtained from uniaxial tensile tests from a porcine small intestine, along with both longitudinal and circumferential directions. Our experiments show decreased stiffness in the circumferential direction. Our simulations show decreased propulsion forces in patients in systemic sclerosis and ulcer patients. As these patients may likely need medical intervention, establishing action concerning the impaired propulsion can help to ease the evaluation and treatment of future complications.

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

Avvari

2021

Meccanica

Self Cite

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Inspired by the feeding mechanisms of a nematode, a novel two-indenter (2I) micropump is analyzed theoretically for transport and mixing of a non-Newtonian fluid for the purpose of lab-on-a-chip applications. Considering that the viscous forces dominate the flows in microscopic regime, the concept lubrication theory was adopted to device the two-dimensional flow model of the problem. By approximating the movements of the indenter as a sinusoidal function, the details of the flow were investigated for variations in -frequency of contraction of the first value keeping the second valve at higher occlusion, and occlusion. The study indicates that occlusive nature of the second valve leads to the large pressure barrier which prevents the fluid to enter into the neighboring compartment. Transport occurs as the lumen opens to develop a suction pressure. Pressure barrier is found to be highest for dilatants followed by Newtonian and pseudo-plastics. Shear stress dependency on frequency the contraction of the first value is highest for lower values of flow behavior index. In conclusion, the study provides details connecting the flows resulting from the indentation of the front-end indenter to the frequency of indentation, geometry and rheology of the fluid, thus facilitating optimal design of the micropumps.

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Effect of local longitudinal shortening on the transport of luminal contents through small intestine

Cited by 16 publications

References 18 publications

Biomechanics of the Small Intestinal Contractions

Biomechanics of the Small Intestinal Contractions

Biomechanical characterization of the small intestine to simulate gastrointestinal tract chyme propulsion

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

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