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WAHuman BiologyQuick questions
Unit 3: Homeostasis and Disease
Quick questions on Pathogens and the immune system: WACE Year 12 Human Biology Unit 3
3short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is the first line of defence (non-specific, external)?Show answer
The first line stops pathogens entering and is non-specific, meaning it acts against anything regardless of type. It includes physical barriers such as the skin and the cilia and mucus lining the airways, and chemical barriers such as stomach acid, lysozyme in tears and saliva, and the slightly acidic skin surface. Useful microorganisms (the normal flora) also compete with pathogens. If these barriers are intact, most pathogens never get inside.
What is the second line of defence (non-specific, internal)?Show answer
If a pathogen breaches the barriers, the second line responds, still without targeting a specific pathogen. Its key features are:
What is the third line of defence (specific immune response)?Show answer
The third line is specific: it targets a particular pathogen by recognising its antigens, and it produces memory. It has two arms, both involving lymphocytes (a type of white blood cell) made in the bone marrow.
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