Non-specific animal defences to pathogens Flashcards
what is quicker, specific or non-specific immune responses?
non-specific
what are the barriers your body has to pathogens?
- skin
- mucous membranes
- lysozymes
how does the skin act as a barrier to pathogens?
it has healthy microorganisms which out compete the pathogens for space on the skin surface
how does the skin prevent growth of pathogen?
it produces sebum which prevents growth
how do mucous membranes act as a barrier to pathogens?
they secrete a sticky mucus which traps microorganisms and contains lysozymes which destroy the cell walls of bacteria and fungi
the mucus also contains phagocytes which remove pathogens
how is a wound sealed in the skin?
a blood clot is formed
when platelets come into contact with collagen in the skin they start to secrete:
- thromboplastin
- serotonin
what does thromboplastin do?
triggers blood clot formation
what does serotonin do?
makes smooth muscle in blood vessel walls contract and reduce the blood flow in the area
what happens when the blood clot dries?
it forms a scab which keeps pathogens out
epidermal cells grow and seal the wound
collagen deposited and eventually the scab falls off and leaves a healed wound
what is an inflammatory response?
localised response to pathogens which causes inflammation
what are mast cells and what doe they release?
cells which when activated release chemicals called histamines and cytokines
how do histamines stop pathogens reproducing?
they cause the blood vessels to dilate which increases the temperature and prevents pathogens from reproducing
how do cytokines get rid of pathogens?
they attract white blood cells which destroy pathogens by phagocytosis
why is a fever useful?
- a fever raises the temperature so that it is higher than 37C which stops most pathogens from reproducing
- the specific immune system works faster at higher temperatures
what are the two types of phagocyte?
- neutrophils
- macrophages
what do phagocytes do?
they are specialised white blood cells which engulf and destroy pathogens
what are the stages of phagocytosis?
- pathogen releases chemicals which attract phagocytes
- phagocyte recognises the non-self antigens on the pathogen
- the phagocyte engulfs the pathogen and encloses it in a phagosome
- the phagosome combines with a lysosome to form a phagolysosome
- enzymes from the lysosome digest and destroy the pathogen
what does a macrophage do which is different to a neutrophil?
it combines the antigens from the pathogen surface membrane and forms the MHC (major histocompatability complex)
the MHC moves the antigens to it’s own surface membrane and it becomes an APC (antigen presenting cell)
what are cytokines?
a chemical used for cell signalling
they can also increase body temp and stimulate the immune response
what are opsonins?
chemicals which bind to pathogens and tag them which makes it easier to be recognised by phagocytes
