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Abstract
Experimental and computational studies suggest a substantial variation in the mechanical responses and collagen fibre orientations of the two structurally important layers of the arterial wall. Some observe the adventitia to be an order of magnitude stiffer than the media whilst others claim the opposite. Furthermore, studies show that molecular metabolisms may differ substantially in each layer. Following a literature review that juxtaposes the differing layer-specific results we create a range of different hypothetical arteries: (1) with different elastic responses, (2) different fibre orientations, and (3) different metabolic activities during adaptation. We use a finite element model to investigate the effects of those on: (1) the stress response in homeostasis; (2) the time course of arterial adaptation; and (3) an acute increase in luminal pressure due to a stressful event and its influence on the likelihood of aneurysm rupture. Interestingly, for all hypothetical cases considered, we observe that the adventitia acts to protect the wall against rupture by keeping stresses in the media and adventitia below experimentally observed ultimate strength values. Significantly, this conclusion holds true in pathological conditions.
Acknowledgements
The authors would like to thank Prof. Peter Hunter from the University of Auckland for making the finite element code CMISS available. P. N. Watton is funded by The Centre of Excellence in Personalized Healthcare (funded by the Wellcome Trust and EPSRC, grant number WT 088877/Z/09/Z). This support is gratefully acknowledged.
Notes
1. The wording mechanical response is used throughout the paper. More precisely it refers to the elastic mechanical response.