Figure 4.

Representation of the three-dimensional collagen fibre orientations throughout the entire thickness of a human abdominal aortic wall (age: 65 years, gender: f). (a) The angles Φ = 0° and 90° denote the circumferential and axial directions of the vessel respectively, the colours correspond to relative amplitudes ranging from dark blue (0%) to dark red (100%). Orientations of preferred fibre directions appear red, whereas blue regions represent orientations with a low fibre density. The striped box on the left indicates the transition layer between the adventitia and the media; I, intima. (b) Changes of relative amplitudes as a function of depth at two representative locations. The dashed black curve corresponds to amplitudes at Φ =+27°, the grey curve at Φ =−27° (0°= circumferential). A similar behaviour of both curves in the adventitia turns into an alternating pattern in the media, indicating a change in the structural organization of collagen fibres between the two layers; from two fibre families in the adventitia to one fibre family with alternating orientations in the media.