The Influence of the Intestinal Unstirred Water Layers on the Understanding of the Mechanisms of Lipid Absorption

Thomson, A. B. R.; Wild, Gary

doi:10.1007/978-1-4615-1195-3_8

Cited by 1 publication

(1 citation statement)

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“…A number of studies have attempted to estimate the UWL thickness, the effective thickness of the diffusion layer. Using 'Michaelis-Menton' kinetic theory (Thomson & Dietschy 1977;Thomson 1979) with permeability data obtained in vitro using rat and rabbit gut tissue and with strong stirring, UWL thicknesses have been estimated as high as 1000 mm in the dog (Frase et al 1985;Thomson & Wild 2001). However, this is physiologically unrealistic.…”

Section: Introductionmentioning

confidence: 99%

A multiscale lattice Boltzmann model of macro- to micro-scale transport, with applications to gut function

Wang

Brasseur

Banco

et al. 2010

Phil. Trans. R. Soc. A.

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Nutrient absorption in the small intestine cannot occur until molecules are presented to the epithelial cells that line intestinal villi, finger-like protrusions under enteric control. Using a two-dimensional multiscale lattice Boltzmann model of a lid-driven cavity flow with 'villi' at the lower surface, we analyse the hypothesis that muscle-induced oscillatory motions of the villi generate a controlled 'micro-mixing layer' (MML) that couples with the macro-scale flow to enhance absorption. Nutrient molecules are modelled as passive scalar concentrations at high Schmidt number. Molecular concentration supplied at the cavity lid is advected to the lower surface by a lid-driven macro-scale eddy. We find that micro-scale eddying motions enhance the macro-scale advective flux by creating an MML that couples with the macro-scale flow to increase absorption rate. We show that the MML is modulated by its interactions with the outer flow through a diffusion-dominated layer that separates advection-dominated macro-scale and micro-scale mixed layers. The structure and strength of the MML is sensitive to villus length and oscillation frequency. Our model suggests that the classical explanation for the existence of villi-increased absorptive surface area-is probably incorrect. The model provides support for the potential importance of villus motility in the absorptive function of the small intestine.

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