Analysis of the strain and stress distribution in the wall of the developing and mature rat aorta (original) (raw)
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Journal of biomechanics, 2011
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Active axial stress in mouse aorta
Journal of Biomechanics, 2012
The study verifies the development of active axial stress in the wall of mouse aorta over a range of physiological loads when the smooth muscle cells are stimulated to contract. The results obtained show that the active axial stress is virtually independent of the magnitude of pressure, but depends predominately on the longitudinal stretch ratio. The dependence is non-monotonic and is similar to the active stress-stretch dependence in the circumferential direction reported in the literature. The expression for the active axial stress fitted to the experimental data shows that the maximum active stress is developed at longitudinal stretch ratio 1.81, and 1.56 is the longitudinal stretch ratio below which the stimulation does not generate active stress. The study shows that the magnitude of active axial stress is smaller than the active circumferential stress. There is need for more experimental investigations on the active response of different types of arteries from different species and pathological conditions. The results of these studies can promote building of refined constrictive models in vascular rheology.
Mechanical properties of rat thoracic and abdominal aortas
Journal of Biomechanics, 2008
Mechanical properties of abdominal and thoracic arteries of 2 mm in diameter were determined from adults Wistar rats. A tensile testing instrument was used to obtain stress/strain curves with arteries immersed in physiological buffer at 37 1C. A displacement was applied on all arteries with various frequencies (1-7.5 Hz) and strains (5-60%). From each curve a Young modulus was obtained using a mathematical model based on a nonlinear soft tissue model. No influence of frequency on modulus was evidenced in the tested range. Abdominal aortas, which were found slightly thicker than thoracic aortas, were characterized by a higher modulus. Due to the interest of decellularized biological materials, we also used SDS/Triton treated arteries, and found that the chemical treatment increased modulus of thoracic arteries. Tensile tests were also performed on thoracic aortas in the longitudinal and transversal directions. Longitudinal moduli were found higher than transversal moduli and the difference could be related to the longitudinal orientation of collagen fibers. These data and mathematical model seem useful in the design of new vascular synthetic or biological prostheses for the field of tissue engineering. r
Atherosclerosis, 2012
Objective-The distribution of atherosclerotic lesions changes with age in human and rabbit aortas. We investigated if this can be explained by changes in patterns of blood flow and wall shear stress. Methods-The luminal geometry of thoracic aortas from immature and mature rabbits was obtained by micro-CT of vascular corrosion casts. Blood flow was computed and average maps of wall shear stress were derived. Results-The branch anatomy of the aortic arch varied widely between animals. Wall shear was increased downstream and to a lesser extent upstream of intercostal branch ostia, and a stripe of high shear was located on the dorsal descending aortic wall. The stripe was associated with two vortices generated by aortic arch curvature; their persistence into the descending aorta depended on aortic taper and was more pronounced in mature geometries. These results were not sensitive to the modelling assumptions. Conclusions-Blood flow characteristics in the rabbit aorta were affected by the degree of taper, which tends to increase with age in the aortic arch and strengthens secondary flows into the descending aorta. Previouslyobserved lesion distributions correlated better with high than low shear, and age-related changes around branch ostia were not explained by the flow patterns.
Assessing the Homogeneity of the Elastic Properties and Composition of the Pig Aortic Media
Journal of Vascular Research, 2001
Most previous studies of arterial wall elasticity and rheology have assumed that the properties of the wall are uniform across the thickness of the media and, therefore, that the relationship between stress and strain may be described by a constitutive equation based on a single strain energy function. The few studies where this assumption has been questioned, focussed on differences between the adventitia and the media rather than on differences within the media itself. Here, we report in vitro elasticity and residual strain measurements performed separately on the inner and outer half of the pig aortic media, together with a histomorphometric assessment of the radial distribution of elastin, collagen and smooth muscle cell numbers. Although we found that the pressure-diameter relationships of the two halves were dissimilar, when allowance was made for their different unloaded dimensions, their material properties agreed closely, a result in keeping with the observed uniform radial...
Biomedical engineering online, 2003
The goal of this work was to determine wall shear stress (WSS) patterns in the human abdominal aorta and to compare these patterns to measurements of intimal thickness (IT) from autopsy samples. The WSS was experimentally measured using the laser photochromic dye tracer technique in an anatomically faithful in vitro model based on CT scans of the abdominal aorta in a healthy 35-year-old subject. IT was quantified as a function of circumferential and axial position using light microscopy in ten human autopsy specimens. The histomorphometric analysis suggests that IT increases with age and that the distribution of intimal thickening changes with age. The lowest WSS in the flow model was found on the posterior wall inferior to the inferior mesenteric artery, and coincided with the region of most prominent IT in the autopsy samples. Local geometrical features in the flow model, such as the expansion at the inferior mesenteric artery (common in younger individuals), strongly influenced W...
Mechanical factors direct mouse aortic remodelling during early maturation
Journal of The Royal Society Interface, 2015
Numerous diseases have been linked to genetic mutations that lead to reduced amounts or disorganization of arterial elastic fibres. Previous work has shown that mice with reduced amounts of elastin (Eln+/−) are able to live a normal lifespan through cardiovascular adaptations, including changes in haemodynamic stresses, arterial geometry and arterial wall mechanics. It is not known if the timeline and presence of these adaptations are consistent in other mouse models of elastic fibre disease, such as those caused by the absence of fibulin-5 expression (Fbln5−/−). AdultFbln5−/−mice have disorganized elastic fibres, decreased arterial compliance and high blood pressure. We examined mechanical behaviour of the aorta inFbln5−/−mice through early maturation when the elastic fibres are being assembled. We found that the physiologic circumferential stretch, stress and modulus ofFbln5−/−aorta are maintained near wild-type levels. Constitutive modelling suggests that elastin contributions to...