1. Atherosclerosis 1
What Causes Atherosclerosis?
Victoria Rock
AIUOnline

2. Atherosclerosis 2
Abstract
In this paper we will discuss the heart and its parts including the arteries, veins, and capillaries.
We will also discuss the diseases Atherosclerosis and Lymphoma and the parts of the human
circulatory system they affect. We will further discuss which circulatory system is better, closed
or open and why.

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What Causes Atherosclerosis?
Atherosclerosis is a disease that affects the arteries of the heart. To understand how
atherosclerosis may cause a heart attack, we must first understand how the heart works.
The heart is made up of four parts, with arteries, veins, and capillaries coming off of it. The
four chambers of the heart are; the left and right ventricles and the left and right atrium, which
each have their part in providing life sustaining blood to all parts of the body. (Audesirk, 2008)
The left and right ventricles are responsible for sending blood out from the heart, while the left
and right atriums are responsible for receiving blood and sending it to the ventricles to be sent
out again. (Audesirk, 2008)
The right atrium and ventricle, referred to as the pulmonary circuit, is responsible for
providing the lungs with nutrients, while the left atrium and ventricle, referred to as the systemic
circuit, is responsible for supplying nutrients to other organs in the body. The coronary circuit
which is another important part of the heart provides blood with oxygen. (Ruck) To simplify, the
right ventricle sends blood to the lungs, after being oxygenated the blood returns to the coronary
circuit where the oxygen and the blood is then sent to the left atrium. The blood is then pumped
from the left atrium into the left ventricle before being distributed throughout the body. The
arteries coming from the left ventricle carries the blood from the heart throughout the body to
other organs, capillaries, forming a web-like network between arteries and veins, receive blood
from the arteries rich in oxygen, exchanging it for carbon dioxide from surrounding tissues and
then dumping the waste-rich blood out to the veins which then returns the blood back to the right
atrium where it is pumped back into the right ventricle and the cycle starts all over again. But if
the arteries become clogged with fat, cholesterol, calcium, and other substances, it forms a
plaque which builds up and hardens causing the arteries to be hard and be inflexible. This is

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called Atherosclerosis disease. This is much the same way as if the pipes in your home become
clogged with grease, food, and hair. When the water can’t flow through, it causes your sinks,
tubs, and toilets to back up. The only difference with arteries is that if the blood can’t go back
through to heart, it dies from lack of blood and oxygen. (Ruck)
Difference between Arteries, Veins, and Capillaries
Arteries, Veins and Capillaries are not that much different from each other. They are all
blood vessels that carry blood through the body. Their differences are in their size and direction
in which the blood flows:
Arteries are fairly large, elastic muscular tubes that carry blood away from the heart to
other body tissues. They are three layers thick in order to withstand the high pressure of
blood being pumped directly from the heart, and are the strongest of the three kinds of
vessels. (Audesirk, 2008)
Veins, like arteries, have three layers but are not as thick or tough as the arteries. Veins
contain valves in them to ensure that blood flows in one direction and doesn’t pool up in
the legs. Veins carry blood from the tissues back to the heart and run parallel to the
arteries throughout the body. (Audesirk, 2008)
Capillaries are thin and fragile, being only one epithelial cell thick and so tight that blood
cells can only flow single file through them. Capillaries are present near almost
everybody cell and re known as the exchange vessels because they allow the exchange of
nutrients and waste between the body’s cells and the blood. They form a web-like
network between veins and arteries. (Audesirk, 2008)

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Advantages of having a closed circulatory system over an open one
Before deciding the advantages of having a closed circulatory system over an open circulatory
system we need to understand what each are:
An open circulatory system is a system in which the heart pumps blood into the hemocoel
which is positioned between the ectoderm and endoderm. With the open system, the
blood flows into an interconnected system of sinuses so that the tissues receive nutrients,
fluid and oxygen directly. With the open system blood volume is high. (Ruck)
In a closed circulatory system blood flows from arteries to capillaries and through veins.
The tissues surrounding the vessels are not directly bathed by blood. A closed system
allows more of a complete function and blood volume is low.
There is a variety of reasons why the closed circulatory system has advantages over the open
circulatory system. One reason is that every cell is at maximum with only two or three cells
distance from a capillary. With closed circulatory there is the ability to have incredible control
over oxygen delivery to tissues. A unique characteristic is the process of ultra filtration in blood
circulation. Also since the lymphatic system is included as part of the circulatory system with its
circulation of excess fluid and large molecules, it decreases the pressure in tissues that extra fluid
increases. Another important advantage is the systemic and pulmonary branches of the system
can maintain their respective pressures. (Ruck)
The Lymphatic System
The lymphatic system works in conjunction with the circulatory system. It collects tissue
fluid, kills foreign organisms, and returns it to the circulatory system. This system also prevents
tissue fluid from accumulating in the tissue space. Lymph capillaries, pick up the intercellular

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fluid and carries it into larger lymph vessels where lymphocytes attack viruses and bacteria, it
than transports lymph to the larger brachiocephalic veins where it re-enters the circulatory
system. (The lymphatic System)
Much like arteries and the disease atherosclerosis, a blockage in the arteries, the lymphatic
system can get a similar disease called lymphoma, which is a blockage in the lymphatic vessels.
Lymphoma’s symptoms are swelling as a result of the obstruction of lymphatic vessels or lymph
nodes, and the accumulation of large amounts of lymph in the affected region. With the inability
to drain fluid properly, resulting in excess fluid in parts of the body, usually the arms or legs,
patients with lymphoma have a higher risk of infection complications because their lymphocyles
cannot reach parts of the body where the swelling occurs. (What Is Lymphedema? What Causes
Lymphedema?, 2010)
Conclusion
The human system is a very complex, yet a simple system, much like the cars we drive, need
regular maintenance to keep them running smoothly. With proper diet and exercise and
following our doctor’s orders, we can prevent many of the diseases like arthrosclerosis and
lymphoma.

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References
Atherosclerosis. (n.d.). Retrieved September 15, 2011, from University of Maryland Medical
Center: www.umm.edu/altmed/articles/atherosclerosis-000016.htm
Audersirk, T. (2011). Chapter 36: Defenses Against Disease. In T. Audersirk, Biology:Life on
Earth with Physiology (9th Ed.) (pp. 691-712). San Franciso: Benjamin Cummings.
Audesirk, T. (2008). Chapter 32: Circulation. In T. Audesirk, Biology-Life on Earth with
Physiology (9th Ed.) (pp. 619-639). San Franciso: Benjamin Cummings.
Ruck, B. (n.d.). Circulatory System. Retrieved September 16, 2011, from Saint Michael's
College, Colchester, VT:
www.cartage.org.lb/en/themes/sciences/zoology/animalphysiology/circulatorysystem/circulatory
system.htm
The lymphatic System. (n.d.). Retrieved September 17, 2011, from Circulatory System-The
Lymphatic System and The Circulatory System:
science.jrank.org/pages/1500/Circulatory-System-lymphatic-system-circulatory-
system.html
What Is Lymphedema? What Causes Lymphedema? (2010, March 2). Retrieved September 17,
2011, from Medical News Today: www.medicalnewstoday.com/articles/180919.php