Diabetes-induced mechanophysiological changes in the small intestine and colon

Table 1 Biomechanical properties of normal small intestine and colon

	Biomechanical properties
Intestine	Tension-strain or stress-strain curves show an exponential behavior[19-23]
	The stiffness differs between the duodenal, jejunal and ileal segments[20,21,24]
	All segments are stiffest in longitudinal direction[20,21,24]
	The opening angle and residual strain shows a large axial variation[25]. The axial variation correlates to the morphometric variation[26]
	The serosal residual strains are tensile and the mucosal residual strains are compressive[24,25,27]
	The residual strains in longitudinal direction are smaller than those in circumferential direction[24], especially on the mucosal side
	The opening angle changes over time for all the small intestine segments. The viscoelastic constant of the rat small intestine is fairly homogenous along its length[28]
	The collagen in submucosa layer is important for the passive biomechanical properties[29,30]
	The villi are important for the biomechanical properties of the small intestine in circumferential direction[31]
Colon	The rat colon has a tensile strength of around 50 g/mm2 and increases in strength from proximal to distal[33]
	Quasi-static P-V curves in colon are approximated to a power exponential function and revealed hysteresis, indicative of viscoelasticity[34]
	The opening angle vary along the rat colon with the highest values in the beginning of the proximal colon[35]. The residual strain is negative at the inner surface and positive at the outer surface[35]
	The stress-strain curves are exponential. All segments were stiffer in longitudinal direction than in the circumferential direction[35]
	In human sigmoid colon, the spatial distributions of the biomechanical parameters are non-homogeneous. The circumferential length, strain, pressure and wall stress increase as a function of bag volume[36]
	The wall stiffness of human sigmoid colon is reduced in response to butylscopolamine[36]
	The phasic and tonic responses to the meal in two colonic regions of human are quantitatively different but qualitatively similar[37]
	Smooth muscle cells in the gastrointestinal tract are constantly being deformed due to forces generated by the muscle cells themselves or by the surroundings[38,39]
	A mechanical creep behavior in the isolated rat colon smooth muscle cells could be described by a viscoelastic solid model[40]