When atherosclerosis develops in any blood vessel of the body, be it
a large artery like the aorta or a small one like a coronary artery, a plaque
forms inside the blood vessel. This plaque is made up of various cells,
macrophages, foam cells (macrophages with
cholesterol in them),
collagen, and free cholesterol. The plaque appears
like a yellow, firm, shiny layer in the inside of a blood vessel.
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The wall of the aorta (and all blood vessels) is a dynamic tissue
made up of living cells, requiring 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.
Primary Medical Reviewer
E. Gregory Thompson, MD - Internal Medicine
Specialist Medical Reviewer
David A. Szalay, MD - Vascular Surgery
January 26, 2010
WebMD Medical Reference from Healthwise
January 26, 2010
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