Human Defence Systems

Question 1

Explain how skin prevents the entry of pathogens:

Answer 1

• Skin covers your body and acts as a barrier
• Platelets help to form a scab to prevent pathogens from getting in
• Skin produces antimicrobial secretions to destroy pathogens

Question 2

Explain how eyes prevents the entry of pathogens:

Answer 2

• Tears contain enzymes which kill bacteria
• Tears are antiseptic

Question 3

Explain how nose prevents the entry of pathogens:

Answer 3

• Full of hairs
• Produces a sticky liquid (mucus), trap pathogens from entering the lungs

Question 4

Explain how the trachea prevents the entry of pathogen?

Answer 4

• Secrete mucus and traps pathogens from the air
• Cilia push mucus to be swallowed

Question 5

Explain how the stomach prevents entry of pathogens?

Answer 5

Produces hydrochloric acid, destroys microorganisms

Question 6

Explain how the immune system prevents entry of pathogens?

Answer 6

Ingesting Microorganisms:
- White blood cells ingest pathogens, digesting and destroying them

Producing Antibodies:
- White blood cells produce antibodies (specific antibody for each antigen)
If pathogens enter again, white blood cell can produce antibodies very quickly to prevent disease

Producing Antitoxins:
- White blood cells produce antitoxins which can neutralise toxins released by pathogens