ATHEROSCLEROSIS OR
ARTERIOSCLEROSIS
Atherosclerosis
or arteriosclerosis refers
to the simultaneous developmentof an atheroma
in an artery and the sclerosis of its wall. An atheroma (from the Greek word
for porridge) is a hard yellow plaque that gradually builds up on the inside of
medium-sized arteries. The plaque consists of a necrotic (dead) core rich in
cholesterol, surrounded by fibrous tissue. Sclerosis (from the Greek word for
hard) means an abnormal hardening or fibrosis, which is the formation of excess
fibrous material within a tissue. Sufferers may experience a sudden heart
attack or stroke, but this belies the fact that in most cases the arteries of
the victims have gradually become blocked by atherosclerosis.
Initially atheromatous plaques start at the site in
an artery where the smooth muscle layer has thickened and been infiltrated with
fibrous connective tissue (fibrosis) when cholesterol and other lipids have
been deposited, and may become calcified. This condition is commonly referred
to as hardening of the arteries. During the course of the disease, the affected
artery expands as the plaque becomes larger so as to allow a more or less
normal flow of blood. However, as the plaque increases in size this becomes
less possible and the lumen of the artery becomes narrower and a ballooning of
the arterial wall causes it to weaken. Also, there is more likelihood of an
embolus becoming trapped in the narrowed artery making the blockage worse.
Healthy arteries are lined with endothelial cells, but the rough lining of a
plaque-damaged artery seems to encourage the adhesion of platelets which means
they are common sites for the formation of a clot (thrombus).
The progresses of atheromatous disease means the
arteries become increasingly occluded and the threat of a heart attack or
stroke increases. Some patients may receive warning in the form of chest pains
if, for example, a coronary artery is partially blocked. The condition known as
angina pectoris (see below) is a
signal that the heart is not receiving sufficient oxygen. This is most likely
to occur when the heart is working hard because of physical or emotional
stress. However, for many people there are no symptoms and they are completely
unaware of their condition until the catastrophic event occurs. Some individuals
have an inherited tendency to develop hypertension, which promotes
atherosclerosis and increases the risk of heart attack or stroke and can cause
chronic damage to the endothelium lining the arteries promoting
atherosclerosis.
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