Non-Specific Defence Systems
Laura Armstrong & Joe Wolfensohn
Teachers
Contents
Recall Questions
This topic requires prior knowledge of the structure and function of specialised cells and tissues in the human body, and basic understanding of how pathogens can enter the body.
What is a pathogen?
A pathogen is a microorganism that causes disease, such as bacteria, viruses, fungi, or protists
Name two ways that pathogens can be spread between people.
Pathogens can be spread through the air (e.g. coughing or sneezing) and through direct contact (e.g. touching contaminated surfaces)
The skin is made of different tissues, what level of organisation is skin?
The skin is an organ
Topic Explainer Video
Check out this @JoeDoesBiology video that explains non-specific defence systems, then read the study notes. Once you’ve gone through them, don’t forget to try the practice questions!
Non-Specific Defence Systems
These are the first lines of defence that act against all pathogens, not targeting specific microbes. They stop the pathogens from entering the blood stream. There are physical and chemical defences.
1. Skin
- Acts as a physical barrier to prevent pathogens entering.
- Produces antimicrobial secretions (e.g. enzymes) that destroy microbes.
- If the skin is cut it produces a scab which stops pathogens from being able to enter the blood.
2. Nose
- Hair and mucus in the nostrils trap particles that may contain pathogens.
3. Trachea and Bronchi
- Specialised cells in the trachea called goblet cells produce mucus which traps pathogens.
- Cilia (small hair-like structures on ciliated cells) move the mucus and trapped pathogens up towards the throat to be swallowed.
- This prevents pathogens from entering the lungs where they could cause lung infections.
4. Stomach
- Contains hydrochloric acid strong enough to kill most pathogens swallowed with food or mucus, this is a chemical defence.
5. Platelets
- Platelets in the blood form clots when the skin is damaged, these clots dry to form a scab - resealing the skin's barrier.
Key Terms and Definitions
|
Term |
Definition |
|
Pathogen |
A microorganism that causes disease. |
|
Non-specific defence |
A general defence that works against all pathogens. |
|
Goblet cells |
Cells in the trachea that produce sticky mucus. |
|
Ciliated cells |
Cells in the trachea with hair-like structures called cilia to move mucus up the airway. |
No answer provided.
Exam Tips
- Don’t confuse cilia (movement) with villi (absorption).
- Cilia are hair like structures found on the surface of cells in the trachea, bronchi and the oviducts.
- Villi are folds of the inner wall of the small intestine where the absorption of nutrients takes place.
No answer provided.
Practice Question
Describe how the human body defends itself against the entry of pathogens. (4 marks)
Model Answer:
- The skin acts as a physical barrier.
- The nose contains hairs and mucus to trap pathogens.
- The trachea and bronchi are lined with cilia and mucus to trap and move mucus and pathogens up to the throat to be swallowed.
- The stomach contains hydrochloric acid that kills most pathogens that are swallowed.
More Practice
Try to answer this practice questions from the TikTok video on your own, then watch the video to see how well you did!