http://www.ck12.org Chapter 1. Human Biology
FIGURE 1.121
This little girl just got her first scraped
knee. It doesn’t seem to hurt, but the
break in her skin could let pathogens en-
ter her body. That’s why scrapes should
be kept clean and protected until they
heal.Other white blood cells attack any pathogens they find. These white blood cells travel to areas of the body that are
inflamed. They are calledphagocytes, which means “eating cells.” In addition to pathogens, phagocytes “eat” dead
cells. They surround the pathogens and destroy them. This process is calledphagocytosis.
White blood cells also make chemicals that cause a fever. Afeveris a higher-than-normal body temperature.
Normal human body temperature is 98.6°F (37°C). Most bacteria and viruses that infect people reproduce fastest at
this temperature.
When the temperature is higher, the pathogens cannot reproduce as fast, so the body raises the temperature to kill
them. A fever also causes the immune system to make more white blood cells. In these ways, a fever helps the body
fight infection.
Vocabulary
- fever: Higher-than-normal body temperature in response to infection.
- inflammation: Response of the body to injury or infection that brings on redness, swelling, and pain.