4.1.1 d non-specific defences

Question 1

how do expulsive reflexes remove pathogens?

Answer 1

vomiting or diarrhoea to expel the contents of the gut
coughs and sneezes to eject mucus

Question 2

how does the skin act as a non-specific defence?

Answer 2

produces sebum which stops the growth of pathogens
covers the body to prevent the entry of pathogens
skin flora of healthy microorganisms that outcompete pathogens for space on the body surface

Question 3

how do the mucous membranes act as a non-specific defence?

Answer 3

secretes sticky mucus
traps microorganisms
contains lysozymes which destroy bacterial and fungal cell walls
contains phagocytes to remove pathogens

Question 4

how does inflammation act as a non-specific defence?

Answer 4

mast cells release histamines and cytokines

Question 5

what do histamines do?

Answer 5

make blood vessels dilate causing redness and heat to stop pathogens from reproducing
also makes the blood vessel walls more leaky to force the tissue fluid out causing swelling and pain

Question 6

what do cytokines do?

Answer 6

attract phagocytes to the site so pathogens can be disposed of

Question 7

what are the stages of wound repair?

Answer 7

the blood clots rapidly with platelets to seal the wound
the clot dries out and forms a hard, tough scab that keeps pathogens out
epidermal cells grow below the scab to seal the wound
damaged blood vessels regrow
collagen fibres are deposited to give the new tissue strength

Question 8

how does the blood clot?

Answer 8

platelets form a plug and initiate the release of clotting factors like thromboplastin
this plasma protein turns prothrombin into thrombin
other clotting factors include calcium ions and vitamin K
thrombin converts soluble fibrinogen into insoluble fibrin which covers the wound

Question 9

what is the role of serotonin in blood clotting?

Answer 9

makes the smooth muscle in the walls of the blood vessels contract so they narrow and reduce the supply of blood to the area

Question 10

what chemicals are a part of the non-specific immune system?

Answer 10

antimicrobial enzymes lysozymes that breakdown the cell wall of bacterium are found in blood, tears, sweat and breast milk
HCl in the stomach

Question 11

difference between non-specific defences and specific defences

Answer 11

non-specific defences are present in humans from birth
rapid response is the same for every pathogen
they do not distinguish between pathogens
not always effective