1. DEFENCE MECHANISMS Key Words WHITE BLOOD CELL,
INGEST, ANTIBODY, ANTITOXIN

2. By the end of the lesson I will:
Objectives
By the end of the lesson I will:
Know a PATHOGEN is a micro-organism that causes an infectious disease
Know pathogens reproduce before they make enough toxins to make you feel ill
Know that the best way to protect ourselves is through the first line of defence (the skin) and not let any pathogens into the body
Identify the second and third line of defence
Know what the white blood cells do to protect your body

3. How do we get sick? Starter
There are four main ways in which you can get sick
Droplet infection – When a sick person coughs, sneezes or talks too close to you
Direct contact – through skin, kissing or other sexual contact
Contaminated food and/or drink – ingestion
Break in the skin – scratches or needle punctures

4. WHAT ARE YOU TRYING TO FIND OUT? WHAT DO YOU EXPECT TO FIND OUT?
I know HOW TO USE ASEPTIC TECHNIQUE
How do we effect change?
We are going to grow some yeast…..
AND THEN KILL IT!
Using ASEPTIC TECHNIQUE infect a petri dish with a yeast solution.
Wait for the solution to slightly dry (perhaps 1hour)
Place a full drop of antiseptic onto the centre of the agar plate.
Incubate for 24-48hours.
WHAT ARE YOU TRYING TO FIND OUT?
WHAT DO YOU EXPECT TO FIND OUT?

5. How many lines of defence do you have in your body?
Skin: Provides both a physical (protective layer that completely wraps around the body, shielding blood vessels, nerves, muscles, organs, and bones) and a chemical barrier (When there is a cut or tear in the surface of the skin pathogens can breach the bodies defence and so glands beneath the skin produce an enzyme that helps kill bacteria) 3

6. Lines of defence 2) Mucous membranes, stomach acid, cilia:
Mucous membranes, produce a sticky substance that traps irritants that enter through the nose.
Structures like tiny hairs, called cilia, line the body's airways and constantly wave foreign particles and mucus away from the lungs to where they can be swallowed safely.
Most harmful microbes that make it to the stomach are destroyed by stomach acids.
Tears and saliva both contain enzymes that destroy invaders.
The brain-blood barrier, a specialized "filter" that surrounds the brain and spinal cord and acts as a physical barrier to keep out proteins, toxins, and most microbes, while letting in glucose, the source of the brain's nutrients.

7. Lines of defence
3) Lymphatic system (white blood cells): You have white blood cells in your body that defend it by
Ingesting pathogens and destroying them (Never EVER say they eat the pathogen as this is WRONG. The only correct word is INGEST)
Some white blood cells produce antibodies that recognise the antigens that are on the surface of the pathogen. The anitbodies of the white blood cell then bind with the antigens of the pathogen which destroys the pathogen or tags it for ingesting by another white blood cell. Each antigen is different and so your body needs to produce an antibody to match each antigen.
Some white blood cells produce antitoxins to counteract the toxins produced by some bacteria. The toxins are bound and destroyed.

8. Lines of defence

9. Use pages 64-65 to complete the Provided worksheets on
Research
Use pages to complete the
Provided worksheets on
‘White Blood Cells’ OR
‘Infection’
Miss will pair you with someone who
you will work with. You will
complete a different sheet each.
You will then have to
teach what you have
learnt to your
partner!

10. By the end of the lesson I will:
Objectives
By the end of the lesson I will:
Know a PATHOGEN is a micro-organism that causes an infectious disease
Know pathogens reproduce before they make enough toxins to make you feel ill
Know that the best way to protect ourselves is through the first line of defence (the skin) and not let any pathogens into the body
Identify the second and third line of defence
Know what the white blood cells do to protect your body