Vascular diseases. Cutaway artwork of a blood clot (lower centre) approaching a junction (centre) of the left carotid artery that has been narrowed by atherosclerotic plaques (yellow). These are fatty deposits of cholesterol on the artery walls. They have caused stenosis (narrowing) of the artery, and if the blood clot lodges (an embolism), then the oxygenated blood supply to the head and brain will be interrupted (occluded). This will cause a stroke, where the brain is damaged due to hypoxia (lack of oxygen). The blood clot (thrombus) may have detached from a site of deep vein thrombosis. The backbone, its nerves (yellow), and skull bones and throat structures are also seen.