In the Injury Theory, it's damage to the arterial endothelium, followed by platelet activation, then smooth muscle cell migration to injury, then macrophages, with resulting "foam cells." Engorged foam cells burst, starting the injury cycle all over again
J. Wills, S. Agarwal, and S. Belongie. Computer Vision and Pattern Recognition, 2003. Proceedings. 2003
IEEE Computer Society Conf. on, 1, page I----37----I----44 vol.1. (2003)
K. von Hayn, R. Werthmann, V. Nikolaev, L. Hommers, M. Lohse, and M. Bunemann. Am J Physiol Cell Physiol, 298 (2):
C324-32(February 2010)von Hayn, Kathrin Werthmann, Ruth C Nikolaev, Viacheslav O Hommers,
Leif G Lohse, Martin J Bunemann, Moritz Research Support, Non-U.S.
Gov't United States American journal of physiology. Cell physiology
Am J Physiol Cell Physiol. 2010 Feb;298(2):C324-32. Epub 2009 Nov
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