Mechanical and Morphometric Changes Along Human Aorta

Aorta is the largest blood vessel in the human body that gradually tapers from descending thoracic aorta to distal abdominal aorta. It acts as a buffering chamber behind the heart to distribute blood to downstream organs and tissues. Arterial physiologic and pathophysiologic behavior is directly linked to their mechanical, morphometric, and structural characteristics. In this work, our goal was to assess changes in mechanical and morphometric characteristics of the aorta along its length. We obtained 8 cadaveric human aortas (average: 33±7 years, 75% female) and characterized their mechanical and morphometric properties at the descending thoracic aorta (dTA), suprarenal aorta (SA), and distal abdominal aorta (dAA) right above the aorta-iliac bifurcation. We then described the experimental stress-stretch response using the four-fiber family constitutive model. Overall, radii, thickness, and circumferential and longitudinal opening angles, which are the measures of residual stresses, decreased along the aortic length. The mechanical properties along the aorta also display regional heterogeneity. In 70% of the samples, dAA was more compliant circumferentially than TA, however, longitudinally, in 43% of the samples, dAA was stiffer than TA which may be due to the presence of atherosclerotic plaques at dAA. These results demonstrated substantial differences in the mechanical and morphometric characteristics of the human aorta along its length. In the future, we will experimentally test more aortas to increase our sample size. We will also determine the physiologic stress-stretch state using constitutive modelling in these specimens and assess the changes in the extracellular matrix microstructure along the aortic tree