Atherosclerosis - Topic Overview
Why does atherosclerosis happen? continued...
Injury may stimulate cells to grow and divide as part of the
inflammatory process. This normal, healing response to chronic injury may
actually result in the growth of atherosclerotic plaque.
This injury could be caused by any number of things, including:
- Physical stress on the artery lining, such as
stress caused by
high blood pressure.
- A response to an
infection within the artery wall.
- Oxidative damage to the artery
lining. Oxidative damage refers to injury caused by unstable molecules called
free radicals. Free radicals are formed during reactions between oxygen and LDL
("bad" or low-density lipoprotein) cholesterol.
- Oxidized LDL
cholesterol may cause injury to the blood vessel wall and promote an
inflammatory reaction that clogs the artery lining with debris. But exactly why high
cholesterol levels promote plaque formation is not clear. Cholesterol is found
normally in all cell membranes, but it may alter the physical properties of the
blood vessel wall, making it more likely to get damaged.
How smoking leads to atherosclerosis
Smoking plays a large role in the development of atherosclerosis. The
carbon monoxide and nicotine contained in tobacco smoke affect blood flow
through your arteries by:
- Making it easier for cholesterol-carrying
lipoproteins to enter the walls of your arteries.
- Promoting the
formation of fibrous plaque.
- Promoting the formation of blood
clots that can completely block your arteries.
How does atherosclerosis cause an aortic aneurysm?
Atherosclerosis is one of the major causes of
The wall of the aorta (and all blood vessels) is a dynamic tissue
made up of living cells that need nutrients and oxygen. Many of these
nutrients seep from the inside of the blood vessel through the walls to nourish
the rest of the blood vessel. When the inner lining of the vessel is covered
with an atherosclerotic plaque, nutrients can no longer seep through
sufficiently. The cells receive no oxygen, and some of them die. As the
atherosclerosis progresses and cells continue to die, the walls become weaker
At some point, a critical relationship is reached between the
pressure experienced in the center of the blood vessel, the wall tension, and
the strength of the wall itself. When this point is reached, the wall begins to
dilate (grow larger) in the area of the plaque. As the diameter of the vessel
grows, the wall tension increases, leading to even more dilation. The end
result is an aneurysm.