S4.4.3 For the adult
The body's defences
Germs are everywhere. Why are we not ill all the time?
What this chapter teaches
The body has two lines of defence. The first keeps pathogens out: skin, mucus with cilia, and stomach acid. The second is white blood cells. Phagocytes take pathogens in and digest them. Other white blood cells make antibodies that fit one antigen. Memory cells give a quicker, bigger response the second time.
Three questions to ask
There is no one right wording. Listen for the idea.
- What are the three parts of the first line of defence?
- What is the difference between a phagocyte and an antibody?
- Why is a second infection by the same pathogen often milder?
After the chapter, the learner can
- Describe skin, mucus and stomach acid as defences
- Explain how white blood cells engulf pathogens and make antibodies
What they copy into their notebook
First line: skin, mucus with cilia, stomach acid. Second line: white blood cells. Phagocytes take pathogens in. Antibodies fit one antigen. Memory cells give a faster, bigger response next time.