The figure on the right has plaque buildup. T he same platelet activity mentioned above can also be initiated by physical injury to the endothelium. Instead of a swollen monocyte, a tiny injury in the endothelium attracts platelets that clump together. However, monocytes will still be attracted to and penetrate the endothelium. This is brought about by the same chemical that platelets secrete to attract smooth muscle.
Cigarette smoke contains chemicals which can damage the endothelial lining.
And increased pressure on arterial walls from high blood pressure may sometimes disrupt the endothelial layer.