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Year 11
OCR
Foundation

Non-specific defences of the human body against pathogens

I can describe defences of the human body against pathogens including physical, chemical and microbial defences, and phagocytosis.

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New
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Year 11
OCR
Foundation

Non-specific defences of the human body against pathogens

I can describe defences of the human body against pathogens including physical, chemical and microbial defences, and phagocytosis.

Download all resources
Share activities with pupils

Lesson details

Key learning points

  1. The human body has defences against infection that work against all pathogens (are not targeted at specific pathogens).
  2. Physical defences include the skin, hairs and cilia.
  3. Chemical defences include tears, saliva and stomach acid.
  4. Microbial defences are provided by microorganisms on, and in, our bodies that compete against pathogens.
  5. White blood cells called phagocytes are part of the immune system and engulf and destroy pathogens by phagocytosis.

Common misconception

All blood cells protect us against pathogens.

White blood cells are part of the immune system that protects us against pathogens. Red blood cells transport oxygen to cells. Platelets are not cells, but they do help to protect against pathogens by helping to seal wounds.

Keywords

  • Pathogen - A microorganism that causes disease.

  • Immune system - A system of defences in the body, including white blood cells, which protects against pathogens.

  • Platelets - Components of the blood which help blood to clot and seal wounds.

  • White blood cell - A type of cell in the blood that is part of the immune system and responds to pathogens.

  • Phagocytosis - When a white blood cell engulfs, digests and destroys a pathogen.

In light micrographs of blood cells, it will be obvious that red blood cells are much more numerous in the blood but white blood cells are nevertheless very important. Point out that white blood cells usually look purple in light micrographs because they have been stained to make them easy to see.
Teacher tip

Equipment

None required.

Content guidance

  • Depiction or discussion of sensitive content

Supervision

Adult supervision recommended

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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Starter quiz

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6 Questions

Q1.
True or false? Pathogens cause disease.
Correct answer: true
false
Q2.
True or false? All microorganisms are harmful to humans.
true
Correct answer: false
Q3.
What is the function of red blood cells?
An image in a quiz
to transport carbon dioxide
to transport hormones
to transmit nerve impulses
Correct answer: to transport oxygen
Q4.
What are proteins made from?
Correct Answer: amino acids
Q5.
Which type of acid does the stomach contain?
An image in a quiz
nitric
ethanoic
Correct answer: hydrochloric
carbonic
Q6.
Diseases caused by pathogens are called __________ diseases.
Correct answer: communicable
non-communicable
lifestyle
genetic

Exit quiz

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6 Questions

Q1.
The human body has defences against pathogens. These include physical defences, defences and microbial defences.
Correct Answer: chemical
Q2.
Match each type of defence to the correct example.
Correct Answer:physical defence,a scab forming to prevent infection

a scab forming to prevent infection

Correct Answer:chemical defence,eyes producing tears that contain enzymes to break down pathogens

eyes producing tears that contain enzymes to break down pathogens

Correct Answer:microbial defence,the microbiota

the microbiota

Q3.
The function of the system is to protect us against pathogens.
Correct Answer: immune
Q4.
Two types of white blood cells are lymphocytes and .
An image in a quiz
Correct Answer: phagocytes, phagocyte
Q5.
Put the steps in the correct order to explain how phagocytosis takes place.
An image in a quiz
1 - Phagocytes are attracted to pathogens by chemical signals.
2 - The cytoplasm of the phagocyte changes shape and engulfs the pathogen.
3 - Enzymes digest the pathogen.
4 - The pathogen is destroyed.
Q6.
Why is phagocytosis described as a non-specific defence?
Correct answer: The phagocytes will engulf any pathogen.
The phagocytes will engulf all cells they encounter.
The phagocytes only engulf one type of pathogen.
The phagocytes will engulf white blood cells.
Q4 lymphocyte: Aldona Griskeviciene/Shutterstock; phagocyte: VectorMine/Shutterstock Q5 VectorMine/Shutterstock