Non-specific animal defences against pathogens - keeping it out

Question 1

What barriers do animals have against pathogens?

Answer 1

skin - flora of healthy microorganisms that outcompete pathogen for space, also produces sebum - oily substance that inhibits growth of pathogens

mucous membrane - traps microorganisms and contains lysozymes and phagocytes

lysozymes in tears, urine and stomach acid to prevent pathogens getting into our bodies

Question 2

What expulsive reflexes against pathogens?

Answer 2

coughs and sneezes eject pathogen-laden mucus from the gas exchange system

vomiting and diarrhoea expel the contents of the gut along with any infective pathogens

Question 3

How are blood clots formed?

Answer 3

skin is breached and pathogens can enter the blood

when platelets come into contact with collagen in skin or the wall of a damaged blood vessel, they ahdere and secrete:

thromboplastin, an enzymes that triggers a cascade of reactions, resulting in the formation of a blood clot

serotonin - makes the smooth muscle in the walls of the blood vessel contract, so they narrow and reduce the blood supply to the area

clot dries and forms a tough scab

Question 4

How is the wound repaired after the blood clot is formed?

Answer 4

epidermal cells below the scab start to grow, sealing the wound permanently

damaged blood vessels regrow

collagen fibres are deposited to givce the tissue strength

once the epidermis reachness noromal thickness, the scab slouughs off and the wound heals

Question 5

What is inflammation?

Answer 5

characteristed by:

pain

heat

redness

swelling of tissue

Question 6

How is inflammation triggered?

Answer 6

mast cells are activated in the damaged tissues and release histamines and cytokines

Question 7

What is the function of the release of histamine?

Answer 7

cause blood vessels to dilate, causing localised heat and redness

the raised temperature helps prevent pathogens reproducing

histamines make blood vessels more leaky so blood plasma is forced out

once force d out the blood it is known as tissue fluid

tissue fluid causes swelling and pain

Question 8

What is the function of cytokines?

Answer 8

attract phagocytes to the sites

they dispose of pathogens by phagocytosis