Hill, Michael
(2012)
A NOVEL APPROACH FOR COMBINING BIOMECHANICAL AND MICRO-STRUCTURAL ANALYSES TO ASSESS THE MECHANICAL AND DAMAGE PROPERTIES OF THE ARTERY WALL.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Elastin and collagen have been described as the dominant passive load bearing proteins in the artery wall. The highly distensible elastin has been hypothesized to bear most of the load at low pressures, with the less distensible crimped collagen fibers uncoiling and thus becoming available to bear load as the overall tissue stretch is increased. Damage to elastin, a microstructural protein responsible for the elasticity of arteries, has been implicated in the pathogenesis of severe cardiovascular events.
To analyze the structure-function relationship of the artery wall and the acute rupture of elastin, new mechanical testing systems were developed, combining uniaxial mechanical testing with non-destructive multi-photon imaging. By using this system to directly measure the distribution of collagen fiber recruitment stretches in the artery wall, a previous conjecture that collagen fibers begin to be recruited at a finite strain was verified. Collagen fiber recruitment was observed to initiate at a finite strain, under increasing extension along the circumference, corresponding to a sharp increase in the measured mechanical stiffness. To quantify this behavior, a new constitutive model was presented in which fiber recruitment begins at finite strain with subsequent individual fiber recruitment represented by a probability distribution function.
Various isotropic models were fit to experimental data obtained from mechanical testing of isolated arterial elastin. Results suggested that a neo-Hookean model used in previous studies is suitable. A new structurally-motivated modeling approach was introduced, directly including structural information regarding the distribution of fenestrae in the internal elastic lamina.
Acute elastin rupture in human cerebral arteries was analyzed with the new system. Elastin was modeled as an isotropic material with a scalar damage variable used to represent acute deformation-induced damage. Microscopic images revealed acute rupture of elastin: the internal elastic lamina was torn to reveal medial collagen underneath. These results provided new insights into the micro-structural and mechanical properties of the artery wall.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
2 February 2012 |
| Date Type: |
Publication |
| Defense Date: |
15 November 2011 |
| Approval Date: |
2 February 2012 |
| Submission Date: |
14 November 2011 |
| Access Restriction: |
5 year -- Restrict access to University of Pittsburgh for a period of 5 years. |
| Number of Pages: |
219 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Bioengineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
artery wall, elastin, collagen, structurally-motivated constitutive models, multi-mechanism, structural damage model |
| Date Deposited: |
02 Feb 2012 15:06 |
| Last Modified: |
02 Feb 2017 06:15 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/10473 |
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