Biomechanical Variation of the Vessel Wall Along the Length of the Healthy Aorta—Linking Geometric, Flow-, and Pressure-Mediated Adaptations

The aorta, the largest artery in the body, exhibits anisotropy and heterogeneity along its length. Over the past several decades, researchers have characterized the positional differences in various geometric and mechanical properties such as wall thickness, diameter, extracellular matrix composition, mechanical properties, opening angle, and axial stretch. These regional adaptations arise in response to various biochemical and mechanobiological stimuli, helping the vessel maintain efficient and resilient blood flow. Early studies, often limited to canine models and uniaxial testing, laid the groundwork for recognizing how composition and mechanics vary with location. Subsequent efforts broadened into comprehensive investigations that included parameters such as wall thickness, diameter, opening angle, and axial stretch, employing diverse animal models and, more recently, human samples. Technological advances in experimental and computational methods have deepened our understanding of these spatial variations, underscoring the aorta's critical role in overall cardiovascular function and its vulnerability to conditions like aneurysms and atherosclerosis. This review seeks to consolidate and interpret these diverse studies on region-specific geometry and mechanics of the aorta, examining how spatial variations arise and how they support normal circulatory function. Further, we argue that any model of aortic growth and remodeling in disease should be able to predict the observed property variation with position in healthy individuals.