A biomechanical model of small bowel motility

A biomechanical model and results of numerical simulation describing the motor activity of small bowel are presented. The organ is modeled on a soft orthotropic cylindrical shell reinforced by the smooth muscle elements of orthogonal type of weaving, embedded in a connective tissue network. The dynamical reaction starts as a response to the depolarization wave propagating along the muscle layers. The muscle layers contract independently but in a coordinated way with the generation of active forces. The mechanical properties of the wall are supposed to be nonlinear. Deformations of the shell are finite. The governing system of equations is solved numerically. The finite-difference method of the second order accuracy over the time and space variables has been used. The dynamics of stress- strain distribution in the shell and shape changes are analysed. It is shown that there is no axial symmetry in the organ´s deformation during the first (preliminary) stage of motor reaction. Only with the development of propulsive contractions is the symmetry observed.