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Unit 19: Biology Part 2 Page 86 of 137
The increased blood flow allows worse for many pathogens. Most
white blood cells (WBC) to come to bacteria and viruses that infect
the infected area. There are people reproduce most rapidly at
several types of WBC’s and all are normal body temperature. With
very important in fighting off the higher temperature caused by
infections and disease. The WBC’s the fever, the pathogens cannot
involved in an inflammation are multiply as quickly.
called phagocytes. Phagocytes
literally means “eating cells” and The Immune System
eating is exactly what these cells
do. The phagocyte engulfs the If a pathogen makes it through
pathogens and destroy them in a both the skin and the second line
process called phagocytosis. defenses, the body begins an
Phagocytosis can also be used for immune response. An immune
“eating” debris in the cell. response is a reaction to pathogens
involving WBC’s called
lymphocytes.
Lymphocytes are so important to
the immune system that this
system is sometimes called the
lymphatic system. In addition to
lymphocytes, the lymph organs –
red bone marrow, the thymus
gland, the spleen, and tonsils – are
very important in this system. The
pictures below illustrate and
Figure 75 – Phagocytosis can describe these organs.
be used to engulf and destroy
pathogens or debris.
WBC’s also produce chemicals that
cause a fever. As you probably
know and have experienced, a
fever occurs when the body
temperature gets above its normal
temperature of 98.6 degrees F (37
degrees C). Although fevers are
no fun for you, they are even
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