Re-examination of the mechanical anisotropy of porcine thoracic aorta by uniaxial tensile tests

Qiang Chen; Yan Wang; Zhi-Yong Li

doi:10.1186/s12938-016-0279-6

Re-examination of the mechanical anisotropy of porcine thoracic aorta by uniaxial tensile tests

Biomed Eng Online. 2016 Dec 28;15(Suppl 2):167. doi: 10.1186/s12938-016-0279-6.

Authors

Qiang Chen¹, Yan Wang², Zhi-Yong Li^{3

4}

Affiliations

¹ Biomechanics Laboratory, School of Biological Science and Medical Engineering, Southeast University, Nanjing, 210096, People's Republic of China. chenq999@gmail.com.
² Biomechanics Laboratory, School of Biological Science and Medical Engineering, Southeast University, Nanjing, 210096, People's Republic of China.
³ Biomechanics Laboratory, School of Biological Science and Medical Engineering, Southeast University, Nanjing, 210096, People's Republic of China. zylicam@gmail.com.
⁴ School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Australia. zylicam@gmail.com.

Abstract

Objective: Considering past studies on the orthotropic anisotropy of arteries in the circumferential and axial directions, this work aims to experimentally study the anisotropic behaviour of arteries by tensioning multi-directional strips of porcine thoracic aorta.

Methods: Histology is first analyzed by staining arterial sections of three orthotropic (axial, circumferential, and radial) planes. 168 stripped samples from 21 aortas are categorized into three loading-rate groups to investigate the influence of loading rates on the Young's modulus and ultimate stress. Basing on the Young's modulus and ultimate stress, the degree of anisotropy is calculated. Moreover, 24 stripped samples from 3 aortas are tested to study the relaxation anisotropy of arteries by fitting the experimental data with a five-parameter Maxwell reduced relaxation function.

Results: Histological analysis shows the parallel orientation of crimpled collagen and elastin fibres. The Young's modulus and ultimate stress reach the greatest in the circumferential direction, and the smallest in the axial direction, respectively, and the values in the other directions are in-between; moreover, the two parameters monotonously increase as the samples orientate from the axial to circumferential directions. The Young's modulus is more sensitive to the loading rate than the ultimate stress. The degree of anisotropy calculated by the Young's modulus is similar to that by the ultimate stress, and it is independent of loading rates. Stress-relaxation also exhibits anisotropy, whose variation is consistent with those of the two parameters.

Conclusions: Due to the stress-growth rule, fibre preferably orientates in the circumferential direction, and the preferable orientation results in great mechanical parameters, anisotropy, and small relaxation behaviour of arteries. The work extends the studies on the arterial anisotropy instead of only the circumferential and axial directions, and could be useful to comprehensively understand the anisotropy of arteries.

Keywords: Anisotropy; Porcine thoracic aorta; Relaxation; Ultimate stress; Young’s modulus.

MeSH terms

Animals
Anisotropy
Aorta, Thoracic / physiology*
Arteries / physiology*
Biomechanical Phenomena
Elastic Modulus
Stress, Mechanical
Swine
Tensile Strength
Viscosity