1. Section 3.6 Protecting the body

2. 3.6 – Protecting the Body
Pathogens – anything that can cause diseases For example: Bacteria, viruses Pathogens cause harm to our cells and tissues. For example: by producing toxins (poison)

3. 3.6 – Protecting the Body
Our body is capable in defending itself from pathogens. In fact, our body has “Two lines of defence”

4. First line of defence
Skin - forms a physical barrier (protection) that keeps many pathogens away. The sweat and oil on our skin is slightly acidic, it can kill or prevent bacteria from growing on us Nostrils – have hair and mucus that traps particles Ear – have wax inside that traps particles

5. First line of defence
Eyes – our tears contain a chemical that can kill some bacteria Stomach – stomach acid can kill some bacteria

6. First line of defence
Our skin, nostrils, ears, and stomach all contribute to our “First line of defence” against pathogens

7. Second Line of Defence
If our first line of defense fails, then our body needs to use its second line of defence Our second line of defence requires our circulatory system

8. Second Line of Defence
Our Circulatory system circulates white blood cells White blood cells are able to detect, capture, and destroy, pathogens

9. Second Line of Defence
Our second line of defence is divided into two types: 1. Innate immune response 2. Acquired immune response

10. Second Line of Defence
Innate Defence is what our body naturally does in order to protect us from pathogens It does not need to be “taught” how to protect us

11. Second Line of Defence
There are 3 steps to the Innate Response Example: the tip of a needle has some disease causing bacteria. And someone pierces your skin with it. Now the bacteria has passed our First Line of Defence!!

12. Second Line of Defence
1. Pathogens will release chemicals that are detected by our body

13. Second Line of Defence
2. Once detected, blood flow will increase, so that more white blood cells are circulated

14. Second Line of Defence
3. White blood cells will engulf (eat) the pathogen and use chemicals to destroy it

15. Second Line of Defence

16. Second Line of Defence The phagocyte is a type of White blood cell
“Phago” means “eating”
Imagine the pathogens are thieves, and criminals; and the white blood cells are the police.
White blood cells are always circulating, looking for pathogens to engulf

17. Second Line of Defence
Acquired Immune Response requires our body to “learn” how to protect us It does this by creating antibodies

18. Second Line of Defence
Acquired Immune Response produces antibodies which recognizes specific antigens Pathogens have antigens that are specific to them Therefore our antibodies are able to identify pathogens

19. Second Line of Defence
If our antibodies detect an antigen that belongs to a pathogen, it will quickly send white blood cells to destroy it Vaccinations can also be used to make our body produce specific antibodies

20. Second Line of Defence
Pathogens all produce a chemical called an antigen When our body detects an antigen, it will create an antibody which is specific to that antigen

21. Second Line of Defence
Antibodies can also recognize toxins and prevent them from harming our cells and tissues This is because antibodies will bind (attach) to the toxin, so that the toxin cannot function properly and becomes harmless

22. Second Line of Defence
*Once antibodies are created, they never go away! Research has shown that there could be as many as 10 million different antibodies in our body*
Antibodies will recognize pathogens and toxins and protect us from them in the future