Ouch! 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. Why?
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. 

• Explain how the skin acts provides protection to underlying tissues from infection and disease.
• Describe what the lymphatic system is and what it does.
• Explain the principles of vaccination and the different types of immunity that it can confer.
• Summarize the hazardous nature of sunburn and of AIDS.

Introduction | Why It Matters | How We Find Out | What We Know | Story Time
Common Hazards | Activities | Self-Study Game | Teachers Pages | Standards (TEKS)