6. Defence Against Infectious Disease Flashcards Preview

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Flashcards in 6. Defence Against Infectious Disease Deck (20):
1

What is a pathogen?

an organism or virus that causes disease

2

What are the body's primary defence against pathogens? How do they work?

- skin and mucous
- by forming a barrier preventing entry

3

How does the skin act as a barrier preventing pathogens from entering the body?

- outer layers of skin are tough and form a physical barrier
- sebaceous glands in the skin secrete lactic acid and fatty acids, which make the surface of the skin acidic. this prevents the growth of most pathogenic bacteria

4

How do mucous membranes act as a barrier preventing pathogens from entering the body? Where are they found? How

- mucous membranes are soft areas of skin that are kept moist with mucus
- Although they do not form a strong physical barrier, many bacteria are killed by lysosome, an enzyme in mucus
- mucous membranes are found in the nose, trachea, vagina and urethra
- in the trachea pathogens get caught in the sticky mucus; cilia then push the mucus and bacteria up and out of the trachea

5

What other defences, apart from skin and mucus, does the body have?

white blood cells:
- phagocytes
- lymphocytes

6

How do phagocytes 'kill' pathogens?

- phagocytes ingest pathogens by endocytosis
- pathogens then killed and digested inside the cell by enzymes from lysosomes

7

Where do phagocytes act?

- in the blood
- can also squeeze out through the walls of blood capillaries and move through tissues to sites of infection. They then ingest the pathogens causing the infection

8

What do large numbers of phagocytes at an infection form?

A SUPER MEGA ULTRA PHAGOCYTE???

pus.

9

What sort of immunity do phagocytes give us? Why?

- non-specific immunity to diseases, because a phagocyte does not distinguish between pathogens - it ingests any pathogen if stimulated to do so

10

Draw and label a phagocyte ingesting some pathogens.

-

11

What happens when the skin is cut and blood escapes from the blood vessels?

a semi-solid blood clot is formed from liquid blood to seal up the cut and prevent entry of pathogens

12

What 'thing' has a critical role in blood clotting? What are they?

- platelets
- small cell fragments that circulate with red and white blood cells in blood plasma

13

How does the clotting process begin? What happens as a result of this?

- with the release of clotting factors either from damaged tissue cells (epithelial cells) or from platelets
- a cascade of reactions in which the product of each reaction is the catalyst of the next reaction

14

What does the cascading system help to ensure?

- that clotting only happens when it is needed
- also makes it a very rapid process

15

What happens in the last reaction in blood clotting? What is the result of this?

- fibrinogen, a soluble plasma protein, is altered by the removal of sections of peptide that have many negative charges
- this allows the remaining polypeptide to bind to others, forming long protein fibres called fibrin (insoluble).
- fibrin forms a mesh of fibres across wounds.
- blood cells are caught in the mesh and soon form a semi-solid clot. If exposed to air, the clot tries to form a protective svab, which remains until the wound has healed.

16

Draw a diagram showing the reactions initiated by clotting factors.

1. reactions initiated by clotting factors released by platelets or damaged tissue cells
2. prothrombin activator (prothrombin (inactive) --> thrombin (active))
3. fibrinogin (soluble) --> fibrin (insoluble)

17

What could happen if deposits of plaque in coronary arteries rupture? What is this called?

- blood clots form (coronary thrombosis), which may completely block the artery
- consequences = an area of cardiac muscle receives no oxygen and so stops beating in a coordinated way

- called: a heart attack

18

What is fibrillation?

uncoordinated contraction of cardiac muscle

(basically a heart attack)

19

Can the heart recover from fibrillation?

- yes, sometimes it starts beating again
- but severe heart attacks can be fatal as contractions of the heart stop completely

20

Sketch and label a diagram of a healthy artery. Sketch and label a diagram of a plaque lined artery. (p76)

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