Organization of Mural Thrombi
J.B. Duguid promoted the idea that atherosclerotic plaques develop from organization of mural or “parietal"  thrombi in the 1940's and 50's . Arterial thrombi tend to remain localized to the low shear environment of the arterial wall because of high blood velocity present on the opposite side of the artery.
Figure 4. This is a mural or parietal thrombus. This is the precursor lesion to the atherosclerotic plaque. Note the eccentric location. This is because the thrombus forms in the area of low shear. The high shear on the opposite wall of the vessel protects that side of the artery from thrombosis.
In the presence of a marked hemodynamic abnormality caused by an obstruction such as an atherosclerotic plaque, an occlusive thrombus can form. In veins, the velocity gradient between the center of the vessel and the vessel wall is small. Thus, thrombi in veins are more likely to become occlusive, as in deep venous thrombosis. This is why atherosclerosis is limited to arteries.
If thrombi persist, whether in arteries or veins, they undergo organization, in which circulating fibrocytes [3, 4, 5] colonize the thrombus and differentiate into cells capable of producing collagen and markers of smooth muscle differentiation, such as smooth muscle actin.
Next Section: Morphology of Atherosclerotic Plaques (Part 5)
1. Majno G, Joris I. Cells, Tissues, and Disease. Blackwell Science, 1996, pp. 634, 648.
5. Caplice NM, Bunch TJ, Stalboerger PG, Wang S, Simper D, Miller DV, Russell SJ, Litzow MR, Edwards WD. Smooth muscle cells in human coronary atherosclerosis can originate from cells administered at marrow transplantation. Proceedings of the National Academy of Science 2003;100: 4754-9.