Gasser, Ogden, Holzapfel, 2006

Model Status

This CellML model was implemented in a manner that could be used for peforming finite element model simulations on the CMISS software program developed at the Auckland Bioengineering Institute, The University of Auckland. The model file presented here focuses on the functional form of the fibre dispersion law corresponding to the the combination 2,4,6,8 (FiberDispersion_law_2468), with 2 representing the isotropic component of the functional form, and 4, 6 and 8 representing the anisotropic components of the fucntional form. For additional information on implementation of cellML files in CMISS, please refer to the following Link. This file has not been recently checked for compatibility within CMISS, any feedback regarding this and any other issues would be appreciated.

Model Structure

Constitutive relations are fundamental to the solution of problems in continuum mechanics, and are required in the study of, for example, mechanically dominated clinical interventions involving soft biological tissues. Structural continuum constitutive models of arterial layers integrate information about the tissue morphology and therefore allow investigation of the interrelation between structure and function in response to mechanical loading. Collagen fibres are key ingredients in the structure of arteries. In the media (the middle layer of the artery wall) they are arranged in two helically distributed families with a small pitch and very little dispersion in their orientation (i.e. they are aligned quite close to the circumferential direction). By contrast, in the adventitial and intimal layers, the orientation of the collagen fibres is dispersed, as shown by polarized light microscopy of stained arterial tissue. As a result, continuum models that do not account for the dispersion are not able to capture accurately the stress-strain response of these layers. The purpose of this paper, therefore, is to develop a structural continuum framework that is able to represent the dispersion of the collagen fibre orientation. This then allows the development of a new hyperelastic free-energy function that is particularly suited for representing the anisotropic elastic properties of adventitial and intimal layers of arterial walls, and is a generalization of the fibre-reinforced structural model introduced by Holzapfel and Gasser (Holzapfel and Gasser 2001 Comput. Meth. Appl. Mech. Eng. 190, 4379-4403) and Holzapfel et al. (Holzapfel et al. 2000 J. Elast. 61, 1-48). The model incorporates an additional scalar structure parameter that characterizes the dispersed collagen orientation. An efficient finite element implementation of the model is then presented and numerical examples show that the dispersion of the orientation of collagen fibres in the adventitia of human iliac arteries has a significant effect on their mechanical response.

The original paper reference is cited below:

Hyperelastic modelling of arterial layers with distributed collagen fibre orientations, T.C. Gasser, R.W. Ogden and G.A. Holzapfel, 2006, Journal of the Royal Society, 3(6), 15-35. PubMed ID: 16849214