Year 9 Science · Unit 1 · Lesson 6
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Learning Goals
Compare two
Complete the table to compare neutrophils and macrophages.
| Feature | Neutrophil | Macrophage |
|---|---|---|
| Lifespan | ||
| Speed of response to infection (when do they arrive?) | ||
| What they do after phagocytosis | ||
| Role in the adaptive (third-line) immune system | ||
| What happens to them in large numbers at an infection site |
Real-world context
On 14 March 2024, a 14-year-old student in Melbourne stepped on a rusty nail at a construction site near their school. The nail punctured the skin on the sole of their foot, potentially introducing soil bacteria including Clostridium tetani and Staphylococcus aureus. Within 6 hours, the wound area was visibly red and warm. By 24 hours, the foot was swollen and painful. By 72 hours, a small amount of pus was visible. The student visited the Royal Children's Hospital, where a doctor assessed the wound and the immune response.
(a) Using the timeline in the scenario, describe what is happening at the cellular and molecular level at each stage (6 hours, 24 hours, 72 hours). Which second-line defence components are active at each stage, and what are they doing?
(b) The doctor told the student that the pus in the wound was a sign the immune system was "working hard." Explain why this is correct, using your knowledge of neutrophils.
1. Mast cells release histamine when they detect damage or infection. Histamine causes blood vessel walls to become more permeable. Explain how histamine contributes to TWO of the four cardinal signs of inflammation.
2. A student with influenza has a temperature of 38.5°C. Their parent wants to give them paracetamol immediately. Using your knowledge of fever as a second-line defence, evaluate whether immediately suppressing a mild fever is always the best course of action.
Wrap Up
In one sentence, what was the main idea of this lesson?