Fig. 8.

A possible mechanism of the radial–circumferential shear occurrence. a When a tensile force (black arrows) is exerted circumferentially to the aorta, collagen fibers bridging ELs are stretched and generate an elastic recoiling force (yellow arrows). A circumferential component of the elastic recoiling force (red arrows) gives radial–circumferential shear to SML. An example is given in (b) where a collagen fiber inclined counterclockwise ψ against the radial direction yields positive (clockwise direction) shear γ. Typical images of c collagen and d elastin fibers in the radial–circumferential plane at 80 mmHg. The elastin fiber image d demonstrates a positive shear in the first and second SMLs from the intimal side (bottom side) where collagen fibers are inclined counterclockwise (c). Negative shear was found in the third SML where collagen fibers lay clockwise