First Line of Defence

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First Line of Defence

Poll

How are you feeling today?

Word Cloud

What is the role of the immune system?

The immune system's job is to protect the body from harmful pathogens.

In order to do this, there are three levels of defence.

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Role of the Immune System

First Line of Defence

The first line of defence is made up of physical and chemical barriers that stop pathogens from entering the body.

It works all of the time and does not need to be 'activated'.

Can you think of any examples? How might your body stop you from getting sick?

Draw this table in your books

​Type	​Mechanism	​How it stops pathogens
​	​Skin	​
​	​Mucus / Cilia	​
​	Reflexes​	​
​	Stomach Acid​	​
​	​Tears / Saliva	​
​	Sweat / Oils ​	​
​	Mucus​	​

Match

Match each barrier to its correct function:

• Skin

• Cilia

• Stomach Acid

• Tears

• Mucus

A tough, waterproof layer

Tiny hairs that push out trapped germs

Contains acid that kills most bacteria

Has enzymes that breaks cell membranes

Traps germs and has enzymes to kill them

• A tough, waterproof layer

• Tiny hairs that push out trapped germs

• Contains acid that kills most bacteria

• Has enzymes that breaks cell membranes

• Traps germs and has enzymes to kill them

Our bodies have harmless (good) bacteria that help defend against pathogens.

Good bacteria help by:

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Good Bacteria

• Take up space so the bad bacteria have no room to grow

• Make chemicals that kill the bacteria

• Break down food and give energy to the rest of our immune system

Multiple Choice

Which of the following is NOT part of the first line of defence?

• Skin

• Stomach Acid

• White Blood Cells

• Tears

Multiple Choice

How does stomach acid help protect the body?

• It traps bacteria like mucus

• It washes bacteria away from the skin

• It kills bacteria that enter through food

• It produces antibodies

Categorize

Options (5)

Skin

Cilia

Tears

Stomach Acid

Good Bacteria

Sort the following defences into physical, chemical, or biological barriers:

Physical

Chemical

Biological

Reorder

Reorder the steps to show how mucus and cilia protect the lungs:

• Mucus traps dust, bacteria, and viruses

• Cilia move mucus upwards towards the throat

• Mucus is swallowed or coughed out

1

2

3

• 1
• 2
• 3

Multiple Choice

True or False: Good bacteria in the gut harm the immune system.

• True

• False

Multiple Choice

True or False: The first line of defence includes white blood cells.

• True

• False