The use of numerical analysis studies in biomechanics research continues to motivate the pursuit of improved models for biological materials. Micropolar continuum theory has been suggested by some to provide more complete descriptions of blood flow and bone behavior. Micropolar theory is an extension of classical continuum theory that introduces independent particle rotations and allows couple stresses. Solutions to relevant modeling problems of current interest are compared for micropolar and classical theory. For blood flowing through a stenosis, micropolar theory yields substantially higher wall shear stresses and slightly more flow recirculation. The extent of deviation from classical theory depends largely upon the choice of boundary conditions for the new independent particle rotation introduced by micropolar theory. In the case of bone behavior, micropolar theory yields significantly different stress fields in the compact bone tissue surrounding the screw hole of a fracture fixation plate. Micropolar solutions reveal higher stress concentrations and markedly increased distortion energy densities. The significant differences between micropolar and classical solutions for the practical modeling problems studied in this work suggest that further experimental and theoretical analyses aimed at better defining micropolar models for blood and bone are warranted.
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