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Plenary Lecture

Plenary 6

Ray W. Ogden (U Aberdeen): Structurally-based analysis of the mechanical properties of soft biological tissues

Thursday, April 21, 2011, 8:30 – 9:15

The continuum mechanics of solids has a key role to play in understanding mechanical factors associated with the normal and pathological functioning of soft biological tissues within the human anatomy.  Essential for applications to the study of, for example, the mechanics of the cardiovascular system is the availability of suitable constitutive models for the description of the mechanical response of the tissues in question, such as the material of the walls of arteries and the heart. Structural constitutive models integrate information about the tissue morphology and therefore permit investigation of the interrelation between structure and function in response to mechanical loading. Tissue structure is often characterized by its anisotropy and this relates to an underlying fibrous structure that generates preferred directions locally within the material. For example, collagen fibres are key ingredients in the structure of arteries, while within the myocardium (the main component of the heart wall) particular directions are distinguished by aligned muscle cells within parallel layers.

In this lecture, we discuss the underlying structure of arterial walls and the myocardium and, on the basis of the nonlinear theory of elasticity, develop a general constitutive framework that can be adapted for the modelling of the passive response of both arterial wall tissue and myocardial tissue, in particular. This incorporates histological information concerning the orientation of collagen fibres and the distribution of orientations within the layers of the arterial wall, or equally, in the case of the myocardium, information about its architecture within which, locally, three mutually orthogonal directions can be identified, forming planes with distinct mechanical properties, so that the myocardium can be regarded as an orthotropic material.

The constitutive models developed within the general theoretical framework yield excellent fits to experimental data from experiments on both artery and myocardial tissue.