Illustration of an atheromatous plaque, fatty build up (yellow) in a medium caliber artery. The plaque slows blood flow, which can cause cardio-vascular complications depending on the location of the plaque. The illustration shows the various layers in the artery. From outside to inside: -the tunica externa or adventitia (two types of tissue, connective and muscular) -the tunica media (two types of tissue, external elastic membrane and smooth muscle) -the tunica intima (three types of tissue, internal elastic membrane, connective tissue and endothelium, single layer of cells around the arterys lumen.) It is in this internal epithelial layer that the artheromatous plaque forms.