M A Lillie1, J M Gosline. 1. Department of Zoology, University of British Columbia, Vancouver, Canada. lillie@zoology.ubc.ca
Abstract
AIMS: This study determines the residual strains on the elastic lamellae in the porcine thoracic aorta to understand the distribution of strains amongst the components of the vascular wall. METHODS: Residual strains in aortic rings were released by cutting and purifying the elastin. Strains were calculated from lamellar contour lengths based on lamellar waviness and from mechanical tests. RESULTS: On the release of residual strains, waviness decreased 2-7%, the inner lamellae shortened 2.1 +/- 0.6% and the outer lamellae shortened 7.1 +/- 0.4% (p < 0.001), indicating that all lamellar elastin was under tension in fresh aortic tissue. Lamellar shortening was 3% greater in the distal than in the proximal tissue. Mechanical tests confirmed the morphological results and showed that the residual strains in fresh tissue required both the elastic tissue and the vascular smooth muscle. Tensile residual strains averaging 1.0% remained in the uncut elastin rings. CONCLUSION: When waviness is considered, the residual strains on the individual wall components can differ from the surface residual strains based only on the ring perimeter. The residual strains on the inner elastic lamellae are tensile, not compressive. The strain distribution amongst the individual components is non-uniform and not adequately understood to determine the physiological strains in the aortic wall.
AIMS: This study determines the residual strains on the elastic lamellae in the porcine thoracic aorta to understand the distribution of strains amongst the components of the vascular wall. METHODS: Residual strains in aortic rings were released by cutting and purifying the elastin. Strains were calculated from lamellar contour lengths based on lamellar waviness and from mechanical tests. RESULTS: On the release of residual strains, waviness decreased 2-7%, the inner lamellae shortened 2.1 +/- 0.6% and the outer lamellae shortened 7.1 +/- 0.4% (p < 0.001), indicating that all lamellar elastin was under tension in fresh aortic tissue. Lamellar shortening was 3% greater in the distal than in the proximal tissue. Mechanical tests confirmed the morphological results and showed that the residual strains in fresh tissue required both the elastic tissue and the vascular smooth muscle. Tensile residual strains averaging 1.0% remained in the uncut elastin rings. CONCLUSION: When waviness is considered, the residual strains on the individual wall components can differ from the surface residual strains based only on the ring perimeter. The residual strains on the inner elastic lamellae are tensile, not compressive. The strain distribution amongst the individual components is non-uniform and not adequately understood to determine the physiological strains in the aortic wall.