Primary defences against disease 4.1.4

Question 1

Why can many pathogens not cause disease?

Answer 1

Due to non specific barriers (physical, chemical) and cellular defences that prevent them from entering

Question 2

What happens if pathogens do enter the body?

Answer 2

The specific immune response prevents them from spreading through the body

Question 3

What line of defence is the skin?

Answer 3

1st

Question 4

Name 3 ways of how skin prevents pathogens from entering the body

Answer 4

• Composed of dead cells containing keratin, which cannot be digested easily = protective barrier to pathogens
• Sebum (sebaceous glands) contain long fatty acid chains - lowers pH and inhibits growth of microorganisms and viruses
• Sweat glands - contain lysozyme which digests cell wall of bacteria

Question 5

How does sebum prevent the entrance of pathogens?

Answer 5

Sebum contains long fatty acid chains which lowers pH and inhibits the growth of microorganisms and viruses

Question 6

How does sweat prevent the entrance of pathogens?

Answer 6

Contains lysozyme which digests the cell wall of bacteria

Question 7

How does keratin in the skin prevent the entrance of pathogens?

Answer 7

It cannot be digested easily and therefore provides a protective barrier to pathogens

Question 8

Where are mucous membranes found?

Answer 8

They line the gut, airways, and reproductive system

Question 9

What does the mucous membrane consist of?

Answer 9

Epithelial cells and mucus-secreting cells like goblet cells

Question 10

What makes mucus sticky?

Answer 10

Many glycoproteins with long carbohydrate chains

Question 11

What is the function of mucus/mucous membranes?

Answer 11

Mucus in the airways can trap particles such as viruses, bacteria, pollen, and dust

Question 12

Where are the ‘air’ particles moved too after being trapped in mucus?

Answer 12

They are moved towards the back of the throat by cilia (small, hair like cells)

Question 13

Name 3 ways the gut defends against pathogens

Answer 13

• HCL acid in stomach - destroys ingested bacteria
• Saliva - lysozyme and amylase
• Gut flora - microorganisms that have a mutualistic relationship with pathogens

Question 14

How does HCL acid defend against pathogens?

Answer 14

It destroys ingested bacteria

Question 15

How does saliva defend against pathogens?

Answer 15

It contains lysozymes and amylase

Question 16

How does gut flora defend against pathogens

Answer 16

They are microorganisms found in the gut which have a mutualistic relationship with pathogens

Question 17

What defences does the urinary/reproductive tract have?

Answer 17

• Semen - spermine is antibacterial
• Vagina - mucus membrane has lactic acid
• Urethra - acidic due to urine

Question 18

How does semen defend against pathogens?

Answer 18

It contains spermine which is antibacterial

Question 19

How does the vagina defend against pathogens?

Answer 19

It has a mucus membrane which has lactic acid

Question 20

How does the urethra defend against pathogens?

Answer 20

It is acidic due to urine

Question 21

What are expulsive reflexes?

Answer 21

Coughing and sneezing, which expel foreign objects and happen automatically

Question 21

How does the nose defend against pathogens?

Answer 21

• Full of hairs and mucus which trap microbes
• Mucus contains lysozymes which break down bacterial and fungal cell walls
• Also contains phagocytes (WBC’s)

Question 22

How does the eye defend against pathogens?

Answer 22

• Protected by tears and rapid eye movement
• Tears contain water, salts, and lysozymes which destroy bacterial cell walls, and microbes usually die in salty conditions

Question 23

What do lysozymes do?

Answer 23

Destroy bacterial and fungal cell walls, by digesting things

Question 24

How does the ear defend against pathogens?

Answer 24

It has yellow sticky ear wax which traps pathogens

Question 25

How does cilia defend against pathogens?

Answer 25

• Mucus traps microbes and ciliated epithelial cells waft it to the back of your throat, then it is swallowed.

Question 25

How does the bladder defend against pathogens?

Answer 25

Urine contains lysozymes!

Question 26

How does the anus defend against pathogens?

Answer 26

• Most microbes are ejected from the anus, and good bacteria out compete the bad bacteria.

Question 27

What are non specific barriers?

Answer 27

They try to destroy any invading pathogen

Question 28

At what temperature do pathogens reproduce best at?

Answer 28

At or below 37°C

Question 28

When does the specific immune system work faster?

Answer 28

At higher temperatures

Question 29

How is normal body temperature maintained?

Answer 29

By the hypothalamus in the brain

Question 30

What happens in the brain when a pathogen invades the body?

Answer 30

Cytokines stimulate your hypothalamus to reset the thermostat and your temperature goes up.

Question 31

What are the steps of the cascade mechanism (blood clotting)?

Answer 31

1. Damaged walls and platelets release, thromboplastin, Ca2+, and vitamin K
2. These combine with prothombin to form the enzyme thrombin
3. Thrombin catalyses the reaction from fibrinogen (which is soluble) to fibrin (which is insoluble)
4. A clot is formed

Question 32

How does inflammation occur?

Answer 32

• Vasodilation
• Blood vessels are more permeable
• WBC leaves the blood vessel
• Histamines are released by connective tissue, WBC, and mast cells

Question 33

What are histamines?

Answer 33

They are released by mast cells/damaged WBC’s
- Cause the blood vessels to dilate causing local heat and redness
- Raised temperature reduces pathogen reproduction
- They make the wall of the capillaries leaky forcing plasma, WBC’s and antibodies out of the capillary - which causes swelling (oedema) and pain

Question 33

What is phagocytosis seen in association with?

Answer 33

Inflammation