The body's defences
Defences come in three lines, in order of speed. First the physical barrier, which prevents most encounters and therefore never gets noticed: unbroken skin, mucus that traps, tears that wash, acid in the stomach. If something crosses it, inflammation and fever come in, which are fast and serve against any intruder. And only afterwards, over days, do tailor-made antibodies arrive, leaving memory cells behind. Almost everything you feel while ill is caused by this response and not by the microbe, which is why bringing the fever down soothes and does not cure. A vaccine kills nothing and replaces nobody: it shows your defences the enemy's face before the meeting, so that next time the response arrives in hours rather than days.
Where this sits
- Comes after
- Viruses, bacteria and contagion
Exercises from this rung
Generated by the app, from easiest to hardest
What is the body's first defence?
- Skin and mucous membranes
- Memory cells
- The antibodies in the blood
- Fever and inflammation
Why The physical barrier, which prevents most encounters and therefore never gets noticed. Unbroken skin, mucus that traps, tears that wash, acid in the stomach. Only when something crosses it do inflammation and fever come in, which are the second line, and only after that antibodies, which are the third and the slow one.
easierWhat is a fever for?
- That sweating washes the infection out
- That the heat burns the microbe directly
- That the body is signalling that you should rest
- That at a higher temperature defences work better and the microbe worse
Why The microbe does not cause it: your own body turns it on deliberately, because a few degrees speed up the defences and hamper many microbes. That is why bringing it down soothes and slightly lengthens the infection. What is worth watching is how high it goes and how long it lasts, not that it happens at all.
in betweenPut an immune response in order.
Answer Something crosses the skin or a mucous membrane, Patrolling cells detect it and raise the alarm, The area inflames and more defences arrive, Antibodies tailored to it are made, Memory cells are left for next time
Why The first three steps are fast and serve against any intruder; the last two take days and are tailor-made. Almost everything you feel while ill — the fever, the tiredness, the swelling — is not caused by the microbe: it is caused by this response. That is why bringing the fever down soothes and does not cure.
harder