teaching this lesson, it will be useful to refer to the Teachers'
Pages before you begin, to give you vital information
associated with this unit.
You've got a splinter in your finger! Since you can't remove all
of it, two days later a small pocket of pus forms around the splinter.
What has happened here?
The splinter has penetrated your body's first line of defense, the
skin. You need the wound to heal. Meanwhile, your body needs to
protect itself from the spread of infection from germs that were
on the splinter. A second line of defense has to be mobilized.
Skin is your first line of defense against "foreign invaders."
If there is a break in the skin, the second-line defenses of the
immune system are activated.
This module will help you
understand how your body reacts to such invasions and what you can
do to help your bodily defenses.