What is Arteriosclerosis?
Arteriosclerosis
is a term used to denote a medical condition characterized by the hardening
and/or
thickening of the blood vessel
walls of the cardiovascular system. When the hardening of the vessels is
accompanied by a buildup of cholesterol along the inner walls, this condition
is referred to as atherosclerosis. Cholesterol and other fatty materials
harden the walls by producing plaque along the inner core
of the vessels. As the vessel
walls become increasingly thicker, the passageways through the vessels
narrow. The net result is
decreased blood supply and increased pressure to the affected region.
This
inelasticity of the vascular component
of the human body affects millions of individuals in our global
community.
The Cardiovascular System
Arteriosclerosis
is just one of many pathological conditions of the cardiovascular system.
In general, the system is composed of the heart and an innumerable assortment
of blood vessels, differing in diameter and elasticity, that course throughout
the body. With the heart acting as a pumping mechanism, this elastic hydraulic
system is a continuous circulatory phenomena.
The Vessels
Blood vessels
transport blood between the heart and the different tissues and organs
of the body. Arteries, arterioles, capillaries, venules, and veins are
all blood vessels. Arteries carry blood away from the heart.
Arteries transport blood from the ventricles to other areas of the body.
They are large diameter vessels that have thick, elastic walls adapted
for carrying blood at very high pressures. Upon closer examination,
the vessels are composed of three layers of endothelial lining. These layers,
the intima, media, and adventitia are the infrastructure and provide the
elasticity for the vascular walls.
Abnormal Arteries
Initially,
in an individual with arteriosclerosis, lesions form along the walls of
the vessels. This results in a blistering effect and an accumulation
of cholesterol and calcium deposits. Over time, the consequences
of this transformation leads to a loss of elasticity and a reduction in
the diameter of the vessels. Due to the reduction in the diameter,
there is decreased blood flow to the affected areas and a buildup of pressure.
Pathologically, the end result is peripheral arterial disease which is
characterized by constriction of vessels throughout the body. When the
pressure exceeds its normal threshold, the lining of the vessels rupture
and results in an event known as an aneurysm. In the event of an
aneurysm, blood flows more slowly through this region resulting in an increase
in pressure in the vicinity of the aneurysm relative to the pressure in
other parts of the artery.
Arteriosclerosis and the
Bernoulli Effect
How
can we understand the dynamic nature of changes that are occurring at this
level? One way to examine these changes is through the Bernoulli
effect:
P + ½pv² + pgy = constant
As blood moves through the vessels of varying cross-section and elevation, the pressure changes throughout the vessels of the body. Bernoulli's equation relates pressure to fluid speed and elevation. According to the Bernoulli principle, as the velocity of a fluid increases, its pressure decreases.
"In
a person with advanced arteriosclerosis, the Bernoulli effect produces
a symptom called vascular flutter. In this situation, the
artery is constricted as a result of accumulated plaque on its inner walls.
To maintain a constant flow rate, the blood must travel faster than normal
through the constriction. If the blood speed is sufficiently high
in the constricted region, the artery may collapse under external pressure,
causing a momentary interruption in blood flow. At this moment, there
is no Bernoulli effect, and the vessel reopens under arterial pressure.
As the blood rushes through the constricted artery, the internal pressure
drops and again the artery closes. Such variations can be heard with
a stethoscope. If the plaque becomes dislodged and ends up in a smaller
vessel that delivers blood to the heart, the person can suffer a heart
attack." (1999, Serway & Faughn, College Physics, p. 278)
Risks and Treatments
An
individual predisposed to arteriosclerosis may have the following risk
factors associated with the disease; diabetes mellitus, obesity, smoking,
and elevated lipid levels in the blood. A genetic predisposition
to abnormal lipid metabolism has proven to be the penultimate risk factor
for the majority of these individuals.
Over
the last few decades, basic scientific research into arteriosclerosis has
been translated into both invasive and noninvasive treatments. Angioplasty,
drugs and weight reduction are just some of these measures. In recent
years, the public health sector has mobilized to promote preventative interventions.
References: The photographs found on this page were copied from the Internet domain. Some of the websites that were cited are http://www.cardio.bayer.com, http://www.encarta.msn.com, http://www.cardiovascular.cx, http://www.heartsite.com, http://www.heartcenteronline.com.