The Physical Processes of Digestion

Introduction

Flow mixing and absorption. The physical problems of extracting nutrients from food items and the possible macroscopic and microscopic solutions. The digestive tube and its limitations. solid to liquid to solid

Methods for evaluating the physical properties of digesta

Particle size

Rheology Viscometry Viscoelastic behaviour Time dependent behaviour

Permeametry

Hindered settling function

Permeability and other measures

Methods for evaluating the relationship between motility and flow of digesta

Solid and liquid phase markers

Reactor mixing

Spatiotemporal mapping

Physical behaviour of fluid digesta

Macroscopic effects Newtonian and non Newtonian behaviour of fluids. Where digesta fit in this system the kinetics of digesta flow Securing efficient absorption from fluids and non-Newtonian fluids, chemical reactor theory and problems

Buoyancy

Backflow form coiled elements

Physical behaviour of solid digesta

The continuum between solids and liquids viscoselasticity securing efficient absorption from fluids and from viscoelastic fluids

Permeability extrusion of the liquid phase

Propulsion and mixing of digesta the interplay between the gut wall and its contents

Tension and stretch receptors in the enteric nervous system

Maintaining the flow of digesta problems of narrowing and expanding

Co-evolution of motility and the physical properties of digesta

Micromixing

Diffusion. Mucus and the unstirred water layer.

Flow in the paravillus space and the crypts.

Tight junctions permeability and fluid flow

Glycocalyceal signalling of shear

The physics of food

What is known about how the physical structure of food interacts with the digestive processes e.g starch granule digestion digestion of proteinaceous aggregates eetc ( Dr Allan Hardacre NZ Crop and Food )

Flow and microorganisms

Adaptions of micro-organisms to move within digesta and mucus

Glycocalyceal signalling

Messing with the properties of digesta

Adulterating foods with viscoactive substances

Nutraceuticals planning the rate of nutrient release. Modulating lumen pressure

Microencapsulation and adherence to the gut wall