Unit 3-Non-Specific Body Defences

Question 1

What is immunity?

Answer 1

The ability of the body to recognise and neutralise or destroy harmful foreign substances in the body like a virus.

Question 2

What are pathogens?

Answer 2

Organisms that cause disease.

Question 3

What does the body defend itself against by means of the immune system?

Answer 3

Disease-causing organisms (pathogens/viruses), some toxins (poisons produced by living things), and cancer cells.

Question 4

What are the 3 lines of defence of the body?

Answer 4

1) Non-specific - physical and chemical defences like skin and saliva/mucus
2) Non-specific - inflammatory response, phagocytosis, natural killer cells.
3) Specific - Lymphocytes, production of antibodies.

Question 5

What do non-specific defences mean?

Answer 5

They work against ANY type of disease causing agent.

Question 6

What do specific defences mean?

Answer 6

That its components each work against a particular pathogen.

Question 7

What are the cells involved in the immune system?

Answer 7

White blood cells, T lymphocytes, and B lymphocytes.

Question 8

What do epithelial cells do?

Answer 8

Epithelial cells form a physical barrier.

Question 9

Where are epithelial cells found?

Answer 9

In the skin and line the respiratory and digestive systems.

Question 10

What do epithelial cells provide?

Answer 10

The first line of defence against any pathogens. As long as they remain intact as they form a protective barrier.

Question 11

Where are lysosomes produced?

Answer 11

In the tears and saliva.

Question 12

What is the defensive effect of lysosomes?

Answer 12

Digest the cell walls of pathogens.

Question 13

Where is acid produced?

Answer 13

Stomach

Question 14

What is the defensive effect of acid?

Answer 14

Destroys microbes that have been swallowed.

Question 15

Where is mucus produced?

Answer 15

Mucus membranes.

Question 16

What is the defensive effect of mucus?

Answer 16

Traps microorganisms.

Question 17

Where is chemical secretions produced?

Answer 17

Sebaceous glands and sweat glands.

Question 18

What is the defensive effect of chemical secretions?

Answer 18

Keeps the pH of the skin at a level too low for most pathogens to grow.

Question 19

When the body suffers a physical injury such as a cut, what is its response?

Answer 19

The body responds with a localised defence mechanism called an inflammatory response.

Question 20

What are mast cells related to?

Answer 20

White blood cells

Question 21

What do mast cells release?

Answer 21

Histamine

Question 22

What does histamine released by mast cells do?

Answer 22

Causes an immune response. It causes vasodilation and increased capillary permeability, resulting in an increased blood flow leading to an accumulation of phagocytes and clotting elements at the site of infection.

Question 23

What are phagocytes?

Answer 23

A type of white blood cell.

Question 24

What do phagocytes do?

Answer 24

They recognise pathogens and destroy them (phagocytosis).

Question 25

What does phagocytosis involve?

Answer 25

The destruction of pathogens by digestive enzymes contained in lysosomes.

Question 26

Following phagocytosis, what do phagocytes release, and what do they do?

Answer 26

They release protein molecules called cytokines. Cytokines attract more phagocytes to the site of infection. Cytokines also signal to the white blood cells of the specific immune system to gather at the site of infection.

Question 27

What is the process of phagocytosis?

Answer 27

1) Phagocyte detects chemicals released by pathogens.
2) Phagocyte adheres to the pathogen.
3) Pathogen becomes engulfed in the cell membrane.
4) Phagocyte forms a vacuole around the pathogen.
5) Lysosomes fuse with the vacuole and releases their digestive enzymes.
6) The pathogen is destroyed by digestive enzymes.