ABSTRACT
An artery adjusts to local asymmetries in flow mechanical forces along its course and around its circumference by adjusting its contour and the thickness of its wall in those segments or regions. The objective is to maintain lumen dimensions for optimal blood flow at all points along its course. Thus, arteries normally have both thin and thick regions and their outer contour ranges between oval and round. Increases in thickness occur through the activation of native intimal smooth muscle cells, which are quicker to respond to such stimuli than medial cells. These increases in wall thickness are selflimited and not to be considered obstructions of the lumen at any age. Increases begin to develop in fetal life 1 and, although variable in degree, are found in everyone at birth 23 . A thick intima is inevitably seen at and near bifurcations of arteries, and at the mouths of even the smallest branch vessels, where it is focal and eccentric. A thick intima is also found at some sites that are not obviously related to a branch vessel, where it is more diffuse. These thick segments are called ‘adaptive intimal thickening’, although many other terms have also been used (see Table 1).
