Lesson 1 ·Class 9 · Aids to Health · Sort Lab
The Body's Local Defences
The barriers a germ meets before immunity is needed.
Sort each defence by how it works.
Sorted 0/10
All items sorted — check each bin.
Free play — sort every item into the bin it belongs in; each correct drop tells you why. Switch to when you're ready to test yourself.
These are all non-specific — they act against any invader, without needing to recognise it first.
What this lesson covers
Challenges to clear
- Fill the Cellular defence bin correctly.
- Sort every defence.
- Fill the Chemical defence box — the body's acids, enzymes and mucus.
The task
Sort each defence by how it works.
What this lesson covers
- Physical barrier: Unbroken skin (A tough keratinised sheet that germs cannot cross unless it is cut.); Mucus lining the nose and airways (It traps dust and germs before they reach the lungs.); Cilia sweeping the trachea clean (They drive trapped mucus upward to be swallowed or expelled.); Blood clotting to seal a cut (It restores the broken barrier and stops germs entering.)
- Chemical defence: Hydrochloric acid in the stomach (It kills most bacteria swallowed with food.); Lysozyme in tears and saliva (An enzyme that dissolves bacterial cell walls.); Sebum and sweat making the skin slightly acidic (Most bacteria cannot multiply at that pH.)
- Cellular defence: White blood cells engulfing germs (Phagocytosis — the cell surrounds and digests the invader.); Pus forming at an infected wound (Pus is dead white cells, dead germs and tissue debris — evidence of a battle fought.); Inflammation — the area becomes red, hot and swollen (Increased blood flow brings more white cells to the site.)
Hint
These are all non-specific — they act against any invader, without needing to recognise it first.