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How Does The Body Fight Infections? |
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Human bodies have a number of
strategies to fight infections or prevent them. The whole of
our infection fighting apparatus is called the “immune
system.” The human body’s immune system doesn’t just include
white blood cells, which attempt to catch and destroy germs,
but a variety of mechanisms that stop germs from creating
infection. |
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An infection, to begin with,
occurs when a healthy person becomes colonized with foreign
species that is hostile to the body. Infections can be
caused by bacteria, viruses, fungi, parasites, prions, and
viroids (virus-like structures).
Firstly, the body has 'barriers' designed to prevent
infection. These barriers are not only physical, but
chemical as well. The first line of defense is the skin; the
skin provides a physical barrier to outside organisms.
Additionally, special cells within the skin layers produce
oils which keep the skin moist and healthy and also control
the population of bacteria colonized on the skin. Remember
that not all bacteria are bad, harmless bacteria live on all
parts of our skin and actually help us by robbing infectious
bacteria of a place to colonize. |
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Because we have other parts of our bodies that are open to
the environment and are not covered by skin, the body
produces chemicals like tears that flush away surface
bacteria and mucus, which traps pathogens until they are
either expelled or killed in the stomach.
If a pathogen makes its way past the physical barriers, then
the body responds through a process called inflammation.
When an area is infected, swelling occurs because blood
vessels dilate to bring extra blood to the area. When
inflammation occurs, the infected cells release chemical
markers that direct white blood cells to the area. |
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White blood cells, also called lymphocytes, are a variety of
specially designed cells with the specific function of
fighting infection. Lymphocytes attack invading organisms
through phagocytosis where the cells actually envelop and
destroy invaders.
Once infected with a particular strain, or variety, of a
pathogen, the body will produce substances called
antibodies. Antibodies work sort of like emergency stop
buttons for invaders, they attach to the pathogen and
immediately disable it. Once antibodies have been formed for
a particular strain, they will always be available for the
rest of the life of the human. The reason that we get more
colds is because there is more than one strain of rhinovirus
(the virus responsible for the common cold). |
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