non-specific body defences

Question 1

explain the bodies physical defenses

Answer 1

Epithelial cells form a physical barrier. They are closely-packed and found in the skin and inner linings of the digestive and respiratory systems.

Question 2

explain the bodies chemical defenses

Answer 2

Chemical secretions are produced against invading pathogens. Secretions include tears, saliva, mucus and stomach acid.

Question 3

state what a pathogen is

Answer 3

A pathogen is a bacterium, virus or other organism that can cause disease.

Question 4

Describe the process involved in the inflammatory response

Answer 4

After injury, mast cells in the connective tissues become activated and release
histamine. Histamine causes blood vessels to dilate and become more permeable. This causes vasodilation of the blood vessels so the injured area becomes red and inflamed.
The stretched capillary walls become more permeable and leak fluid into neighbouring tissues.

Question 5

Describe what the increased blood flow leads to in the inflammatory response

Answer 5

The increased blood flow leads to an accumulation of phagocytes and clotting elements at the site of infection.

Question 6

Explain how phagocytes destroy pathogens

Answer 6

Phagocytes recognise pathogens and destroy them by phagocytosis.
Phagocytosis involves the engulfing of pathogens and their destruction by digestive enzymes contained in lysosomes.

Question 7

Explain what cytokines are and why phagocytes release them

Answer 7

Cytokines are protein molecules that act as a signal to specific white blood cells causing
them to accumulate at the site of infection.
Phagocytes release cytokines which attract more phagocytes to the site of infection.