Lesson 4 of 16
The body's own defences
Show on a big screenThe airway is the breathing passages. Do skin, the airway and stomach acid stop every germ?
Step 1 of 4
- A batch of germs arrives at three gates: skin, airway, stomach.
- Each gate stops many of the germs.
- A few still get past each gate.
- What got past meets the immune system inside.
No. Each one stops many germs. A few still get past.
A barrier is anything in the body that stops germs.
Immunity is how well the body fights a germ. The immune system does this work inside the body.
The rule
Skin, the airway lining and stomach acid are barriers in the body. Each stops many germs, but not all. Germs that get past meet the immune system inside.
| Barrier | Where | What it does |
|---|---|---|
| Skin | All round the outside | Blocks germs that land on it |
| Airway lining | The breathing passages | Sticky; traps germs |
| Stomach acid | The stomach | Kills many swallowed germs |
The germs here are made-up bench units, not a real body.
Switch the barriers on and off. Watch the count inside.
Loading lab…
Try the lab to finish this lesson.