Internal non-specific defences

Question 1

What are the two internal non-specific defences?

Answer 1

Inflammation and fever.

Question 2

What is the process of inflammation?

Answer 2

1) Mast cells are activated by chemokines and release histamines (1a) and heparins (1b)
1a) Histamines target capillaries and increase blood flow to the site of infection (heat and redness), increase permeability of capillaries (swelling)
1b) Heparins prevent immediate clotting in the area, instead creating a fluid clot to prevent the spread of pathogens.

2) Chemokines attract phagocytes to target pathogens at area of infection. Triggers release of pyrogens.
3) Pain receptors in the skin are stimulated
4) Pus is produced, formed from dead phagocytes and tissue fluid.
5) New cells are produced via mitosis, which repair and replace damaged cells.

Question 3

What is the process of fever?

Answer 3

1) Pyrogens are released from leukocytes, and “reset the body’s thermostat” to a temperature of +/-39C
2) The body feels cold and takes steps to conserve heat, such as vasoconstriction, shivering and behavioural changes. This causes the body temperature to rise to +/- 39C
3) Body temperature reaches 39C - the “crisis point”. This causes the fever to break, and the body’s thermostat resets to 36.8C
4) The body feels hot and takes steps to release heat, such as vasodilation, sweating and behavioural changes. This causes the body temperature to return to 36.8C

Question 4

Name the two main cells involved in inflammation and describe how they arrive at the site of inflammation.

Answer 4

Leukocytes (white blood cells)
Move through the bloodstream.

Macrophages
Remain fixed or wander through various tissues.

Question 5

What are the four stages of phagocytosis?

Answer 5

1) Attachment
2) Engulfing
3) Killing
4) Degradation

Question 6

What are the four symptoms of inflammation?

Answer 6

Swelling
Redness
Heat
Pain

Question 7

Define the structure and function of the lymphatic system.

Answer 7

Network of one-way blind-ended lymph capillaries, which join up to form lymphatic ducts, which re-enter into the circulatory system. Lymph nodes are found along this pathway (e.g. neck, armpit)
Much smaller than veins and arteries

Collects excess tissue fluid and returns it to the circulatory system
Concentration of immune cells at nodes - functions to help prevent infection

Question 8

What cells are found in the lymph nodes? Explain the structure of a lymph node.

Answer 8

Immune cells (e.g. macrophages, lymphocytes, plasma cells)

Criss-crossed network of fibres, which filters pathogens

Question 9

Provide examples of man-made mechanical barriers.

Answer 9

Face masks
Latex gloves
Safety goggles

Question 10

Define non-self in the context of immunity.

Answer 10

Any foreign agent not recognised as being part of the body

Question 11

Define a macrophage.

Answer 11

White blood cell
Phagocyte
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