Although the exact biological process is not completely understood,
scientists have described three different stages of atherosclerosis that lead
to the "clogging" of your arteries.
The fatty streak: The
first evidence of atherosclerosis can be found in children 10 to 14 years of
age. The "fatty streak" appears as a yellow streak running along the major
arteries, such as the aorta. The streak consists of smooth muscle cells, which
are filled with cholesterol, and macrophages (a type of immune system
"scavenger" cell that removes harmful substances, such as excess cholesterol
particles, from the bloodstream). The fatty streak alone does not cause any
symptoms but, over time, can develop into a more advanced form of
atherosclerosis called fibrous plaque.
Fibrous plaque: A fibrous plaque forms in the inner layer of the artery. The
plaque consists of large numbers of smooth muscle cells, macrophages, and
lymphocytes (a type of white blood cell that typically responds to an infection
or injury). These cells are all filled with cholesterol. As the fibrous plaque
grows, it projects into the space inside the artery where the blood is flowing.
Complicated lesion: The last stage of
atherosclerosis occurs when the fibrous plaque breaks open, exposing the
cholesterol and connective tissue underneath. This rupture provokes a strong
clotting reaction from your blood, such as when you have a cut. The combination
of fibrous plaque and the blood clot is called a complicated lesion.
It narrows your arteries.
When the fibrous plaque grows large enough, it begins to narrow your arteries.
This narrowing process happens slowly over many years. In time, the plaque
growing into your arteries can limit blood flow to such a degree that parts of
your body that depend on the arteries for blood begin to suffer from lack of
oxygen, a condition called ischemia. When fibrous plaque in your coronary
arteries causes your heart muscle to suffer from lack of oxygen, you may
experience chest pain (angina).
It hardens your arteries. When hard plaque forms in the walls of an artery, it can
restrict the artery's ability to widen (dilate) so that more blood can flow
through when needed, such as when you physically exert yourself. This
"hardening" of your coronary arteries can also cause chest pain, usually during
It blocks your arteries. When a
blood clot forms around a crack or rupture in the fibrous plaque, this
complicated lesion can completely block the flow of blood through the artery.
Such an abrupt loss of blood supply causes lack of oxygen to or actual death of
tissue (infarction), which can then damage tissues or organs that normally
receive blood from that artery. Men who smoke and/or have high cholesterol have
a greater chance of having a plaque rupture, causing a heart attack or sudden
The role of smoking
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.
formation of fibrous plaque.
Promoting the formation of blood
clots that can completely block your arteries.
If you think of atherosclerosis as a response to injury, the buildup
of fibrous plaque can be reversed by removing the source of injury. In the case
of high cholesterol, by reducing the amount of LDL cholesterol in your arteries
and increasing the amount of HDL, which removes cholesterol that is already in
your artery walls, you can actually reverse atherosclerosis. The ability to
reverse atherosclerosis helps explain why treating high cholesterol can reduce
the risk of further complications from atherosclerosis.
Primary Medical Reviewer
E. Gregory Thompson, MD - Internal Medicine
Specialist Medical Reviewer
Carl Orringer, MD - Cardiology, Clinical Lipidology
July 2, 2010
WebMD Medical Reference from Healthwise
July 02, 2010
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