ABSTRACT
The next layer of an artery is the tunica media or simply media. It surrounds the internal elastic lamina and its composition depends on the type of artery. Large arteries have additional circumferential layers of elastic tissue within the media and are thus referred to as elastic arteries. The epicardial coronary arteries are elastic arteries as are the carotids, cerebral arteries and the aorta. However, at the point the epicardial arteries turn into the myocardium, usually at a right angle from the parent vessel, they become more muscular arteries with few if any elastic fibers. In normal arteries, the vessel lumen diameter can be altered by contraction or relaxation of the medial vascular smooth muscles in response to a variety of systemic signals and locally released factors. However in certain disease states, such as restenosis following balloon angioplasty, growth and hypertrophy with migration into the intima are the usual responses (8).
