Figure 3.

Volume-rendering of optical sections through an entire aortic wall acquired using second-harmonic generation imaging. The left panel shows a radial projection (circumferential/radial plane; x–z) highlighting fibrillar collagen throughout the thickness of a human abdominal aortic wall (age: 65 years, gender: f). The three smaller panels on the right are in-plane projections (circumferential/axial plane; x–y) from regions inside the adventitia (I), media (II) and intima (III), indicated by the red boxes in the left panel. Note the marked differences in collagen fibre morphology between the three arterial layers. Generally, the adventitia displayed characteristic fibre bundles, often organized as two counter-rotating fibre families oriented mostly between the major vessel axes; in the media, the fibre bundles changed into one fibre family, organized in a layered structure with alternating orientations closer to the circumferential direction. The intima of this vessel was characterized by a mostly isotropic organization of collagen fibres, whereas intimas of other vessels also displayed anisotropic fibre morphologies.