non specific defence Flashcards
what are primary defences
physical and chemical defences that prevent entry pathogen into body
non specific as work the same for all pathogens
what are the primary defences
skin
mucous membranes
explusive reflexes
tears
wax in ear canal
non pathogenic bacteria
mucous membrane role in primary defence
- line parts body contact pathogen eg airway/ digestive tract
- mucus secreted from goblet cells, has antimicrobial enzymes
-cilia waft mucus away airway
expulsive reflex role in primary defence
-cough/ sneeze
- automatic
- expel foreign bodies
skins role in primary defence
- outer layer dead cells with keratin
- low moisture, pH and high salinity prevent microorgs replicating on skin
non specific secondary defences
blood clot
inflammation
phagocytes
tears role in primary defence
have lysosomes which are antibacterial
what is secondary defences
responds to pathogens that have passed primary defence
still non specific as dont distinguish between different pathogens
non pathogenic bacteria role in primary defence
in digestive tract to compete with pathogens
wound repair role in secondary defence
- blood clot
- form scab to allow new layer skin form
how does blood clot
collagen exposed - release clotting factors
inactive thrombokinase to active thrombokinase
active TBK with calcium to active prothrombin to thrombin
thrombin catalyses conversion soluble fibrinogen to insoluble fibrin
fibrin forms mesh trapping RBC
clot forms
new cells grow
tissue contracts to draw edges wound together
new blood vessels form
inflammations role in second line of defence
mast cells secrete histamine causing:
vasodilation so blood flow inc
- hotter to prevent reproduce pathogens
capillaries more leaky flushing pathogens to tissue fluid
- swelling (odema)
pathogens leave blood and enter tissue fluid
histamines stimulates cells to secrete cytokines to encourage phagocytes to area
role of neutrophils
circulate in blood
rush to infection site and engulf pathogens
die and accumulate as pus
come from bone marrow
lobed nucleus
role of fever
higher temp inhibits pathogen reproduction
specific immune system works faster
phagocytes role in second line defence + 3 types
engulf pathogens and foreign material
neutrophils/macrophage/dendritic
role dendritic cells
long processes for large SA
take foreign material to lymph nodes
Antigen presenting
near surfaces
what is the third line of defence
fever
phagocytosis
role phagocytosis
phagocytes engulf and destroy pathogens
collect at site infection
role of macrophage/monocyte
enter tissue fluid where form macrophages
long lived
present antigens to lymphocytes
stages of phagocytosis
- phagocyte recognises non self
- engulfs pathogen form phagosome (invagination of plasma membrane by cytoskeleton)
- lysosomes combine with phagosome to form phagolysosome
- digestive enzymes in lysosome breaks down pathogen
- digested material absorbed and waste released
- can display antigens
what are cytokines
cell signalling molecules
stimulate other phagocytes to area
inc body temp + stim specific response
what are opsonins
chemicals that bind to pathogens and ‘tag’ them for easy recognition by phagocytes
phagocyte has receptors complementary to opsonin allowing easier phagocytosis
how does APC work
antigen combines special protein complex and placed on apc plasma membrane
