Variations in stiffness and structure of the human aorta along its length

This study provides a detailed analysis of the regional mechanical, structural, and morphological variations of the human aorta using freshly excised tissue from 10 middle-aged and elderly donors. Samples from four anatomical regions—the descending thoracic, supraceliac, infrarenal, and distal abdominal aorta—were subjected to planar biaxial mechanical testing, morphometric analysis, and histology. The results revealed a progressive distal stiffening associated with decreasing elastin density (from 23.5% to 8.9%), fragmentation of elastic lamellae, and reduced circumferential and longitudinal stretch ratios. Constitutive modeling using four material models showed that a four-fiber family model best described the aortic stress–strain response, providing region-specific material parameters for computational modeling and medical device design.