Example 1
Match mucus, a phagocyte and a natural killer cell to their roles.
Mucus traps particles; a phagocyte engulfs material; a natural killer cell can kill certain abnormal host cells.
Year 11 · SACE Stage 1
Barriers and innate defence
Match first-line barriers and innate components with their functions.
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Method and worked examples
Intact skin provides a physical barrier. Mucus traps particles, cilia help move trapped material away, tears contain antimicrobial substances, and stomach acid inhibits many swallowed microbes. These mechanisms reduce entry but do not prevent every infection. If entry occurs, innate responses recognise broad danger or pathogen-associated patterns and respond without requiring previous exposure to that specific agent.
Phagocytes engulf and digest material. Inflammation increases local blood flow and changes vessel permeability, helping recruit defensive cells and proteins. Complement proteins can promote inflammation, coat targets for uptake or damage suitable microbial membranes. Natural killer cells can destroy certain infected or abnormal body cells. Innate mechanisms occur widely among organisms; plants have barriers and innate responses but not the same lymphocyte-based adaptive system as humans.
Example 1
Example 2
Why is local swelling consistent with inflammation?
Increased vessel permeability allows fluid and defensive components to enter tissues, contributing to swelling.
Watch out: Innate responses can act on first exposure using broad recognition mechanisms; pathogen-specific memory is a central adaptive feature.