Part 4: Defence Mechanisms

Question 1

Describe how the nose prevents pathogens from entering.

Answer 1

Sneezing - the mucus and nostril hairs in your nose trap particles that may contain pathogens or irritate your lungs.

Question 2

Describe how the stomach prevents pathogens from entering.

Answer 2

Kill bacteria

Question 3

Describe how the skin prevents pathogens from entering (2)

Answer 3

1. The skin covers the body and acts as a barrier from bacteria and viruses
2. Healthy skin is covered with microorganisms that keep you healthy and act as an extra barrier to the entry of pathogens

Question 4

Describe how the trachea and bronchi prevent pathogens from entering the body. (2)

Answer 4

1. The trachea and bronchi secrete mucus that traps pathogens from the air.
2. The lining of the tubes is covered in cilia (tiny hair-like projections from the cells)

Question 5

Describe how tears and ear wax prevent pathogens from entering the body.

Answer 5

Contain the enzyme ‘lysozyme’ which kills bacteria.

Question 6

Explain how bacteria makes us feel ill.

Answer 6

Produce toxins or cause damage to the cells

Question 7

Explain how viruses make us feel ill.

Answer 7

Cause damage to cells when they reproduce.

Question 8

What are the two types of white blood cell called?

Answer 8

1. Phagocytes
2. Lymphocytes

Question 9

Define ‘immune system’.

Answer 9

The body system which recognises and destroys foreign cells or proteins, such as invading pathogens.

Question 10

Define ‘antibody’.

Answer 10

A special protein produced by lymphocytes, which binds to specific antigens found on the surface of specific bacteria or viruses, which then targets them for destruction.

Question 11

Define ‘antitoxin’.

Answer 11

A protein produced by lymphocytes, which binds to and counteracts (cancels out) toxins released by pathogens.

Question 12

Define ‘phagocytocis’.

Answer 12

When a pathogen is engulfed, then destroyed by a phagocyte.

Question 13

Describe the functions of lymphocytes. (2)

Answer 13

1. Produce antibodies that bind to pathogens, targeting them for destruction.
2. Produce antibodies that counteract toxins produced by bacteria

Question 14

Describe the function of phagocytes.

Answer 14

They engulf and destroy bacteria

Question 15

Describe the function of the immune system. (4)

Answer 15

1. Pathogen enters the bloodstream
2. Lymphocytes produce antibodies that bind to pathogens, targeting them for destruction.
3. Antibodies bind to antigens on pathogens/ antitoxins bind to toxins.
4. Phagocytocis of pathogens or toxins

Question 16

Explain how blood not clotting properly increases your risk of getting infections. (2)

Answer 16

1. Pathogens will have easier access to your bloodstream
2. Clotted blood prevents pathogens from entering the body through cuts in the skin.

Question 17

Explain how a decrease in the number of white blood cells in the body increases the risk of getting infections. (3)

Answer 17

1. More toxins and pathogens will be able to enter the bloodstream without being detected.
2. Phagocytocis will take place less often.
3. White blood cells destroy pathogens.

Question 18

Why are diseases spread easily in refugee camps? (7)

Answer 18

1. Close contact with strangers (overcrowding)
2. Unprotected sex (leads to STDs)
3. Contaminated food
4. Lack of clean water
5. If in a hot climate, then insects like mosquitoes
6. Lack of access to basic hygiene
7. Poor diet
8. When people come from different areas, they have different variants of illnesses.