AQA · GCSE · Biology
Course version: 8461 · Version from Sept 2018
Students should be able to describe the non-specific defence systems of the…
Full specification wording
Human defence systems: Students should be able to describe the non-specific defence systems of the human body against pathogens, including the: • skin • nose • trachea and bronchi • stomach.
Non-specific defences stop pathogens entering the body or trap and destroy them before they cause infection.
Checked against the AQA 8461 specification (opens in a new tab) on .
- Point 1 of 4
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Non-specific defences stop pathogens entering the body or trap and destroy them before they cause infection. They are not tailored to one pathogen. The skin is a physical barrier: its outer layer of dead cells is tough, and glands secrete antimicrobial substances. The nose has hairs and sticky mucus that trap particles and microorganisms in inhaled air. In the trachea and bronchi, ciliated epithelial cells beat mucus, with trapped pathogens, upwards towards the throat to be swallowed. The stomach contains hydrochloric acid, which is very acidic and kills many pathogens that are swallowed in food, drink or mucus. Together these defences reduce the chance of pathogens reaching tissues where they could multiply.
What earns the marks
- Non-specific defences act against many pathogens and are not targeted at one specific pathogen.
- The skin acts as a physical barrier and produces antimicrobial secretions.
- The nose traps pathogens using hairs and sticky mucus.
- The trachea and bronchi are lined with cilia that move mucus containing pathogens away from the lungs.
- The stomach produces hydrochloric acid, which kills many swallowed pathogens.
- Mucus and cilia work together to remove pathogens from the airways.
Common mistakes and how to put them right
Calling these defences specific to one pathogen.
Put it right: They are non-specific and act against many pathogens.
Saying cilia trap pathogens.
Put it right: Mucus traps pathogens and cilia move the mucus.
Saying the stomach produces enzymes that kill pathogens.
Put it right: Hydrochloric acid kills them.
Exam tips
- Name each defence and state exactly how it stops pathogens, using the correct structure.
- Use the words mucus and cilia accurately and link them to the airways.
- For the stomach, name hydrochloric acid rather than just saying acid.
Try the lesson
The start of the Human defence systems: Students should be able to describe the non-specific defence systems of the human body against pathogens, including the: • skin • nose • trachea and bronchi • stomach. lesson, made from checked teaching notes for this specification point.
Have a go first
Which part of the human body acts as a physical barrier that stops pathogens entering the blood?
Listen
Non-specific defences stop pathogens entering the body or trap and destroy them before they cause infection. They are not tailored to one pathogen. The skin is a physical barrier: its outer layer of dead cells is tough, and glands secrete antimicrobial substances. The nose has hairs and sticky mucus that trap particles and microorganisms in inhaled air. In the trachea and bronchi, ciliated epithelial cells beat mucus, with trapped pathogens, upwards towards the throat to be swallowed. The stomach contains hydrochloric acid, which is very acidic and kills many pathogens that are swallowed in food, drink or mucus. Together these defences reduce the chance of pathogens reaching tissues where they could multiply. A strong answer earns marks for these points. Non-specific defences act against many pathogens and are not targeted at one specific pathogen. The skin acts as a physical barrier and produces antimicrobial secretions. The nose traps pathogens using hairs and sticky mucus. The trachea and bronchi are lined with cilia that move mucus containing pathogens away from the lungs. A common slip: Calling these defences specific to one pathogen. Instead, they are non-specific and act against many pathogens. Exam tip: Name each defence and state exactly how it stops pathogens, using the correct structure.
See it
Key words
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Non-specific defences
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Skin
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Nose
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Stomach
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See every definition
- Non-specific defences
- Defences that act against many pathogens and are not targeted at one specific pathogen.
- Skin
- Acts as a physical barrier, with an outer layer of dead cells that is tough, and glands that secrete antimicrobial substances.
- Nose
- Traps pathogens using hairs and sticky mucus in inhaled air.
- Stomach
- Produces hydrochloric acid, which is very acidic and kills many swallowed pathogens.
Label the diagram
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1Box 1
2Box 2
3Box 3
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