Figure 2

Predicted wall stress with explicit inclusion of elastic lamellae and intra-lamellar regions. (a) The bulk behavior of the aorta predicted by passive (dashed black line) and active (solid, black line) SPH models agrees well with an analytical passive solution for a homogenized media (dashed, grey line) and a semi-analytical active solution determined by adding active stress to the passive SPH result (grey, solid line). Vertical and horizontal dashed lines show the homeostatic in vivo configuration. Note the 23% reduction in outer diameter at the homeostatic pressure (102 mmHg) caused by SMC activation. (b,c) Transmural distributions of circumferential and radial Cauchy stress through the thickness in the passive and active models, respectively. The red circle, blue square, and green triangle correspond to medial elastin, medial intra-lamellar, and adventitial particles, respectively; the vertical dashed line shows the medial-adventitial border in the current configuration. The highly non-uniform distribution of stress through the wall is attributed to different properties of the elastic lamellae and intra-lamellar regions. Active stress generation by SMCs elevates stress in the intra-lamellar particles but, because of the reduction in the diameter, decreases stresses in the medial elastin and adventitial particles relative to those in the passive case. Note that the assumed deposition stretches tend to reduce transmural gradients, especially in the homeostatic state, by introducing residual stresses (not shown).