To cause disease, it
must: Gain entry to host,
Colonise tissues of host,
Resist defences of host,
Cause damage to host
tissues
Entry to body
Interfaces
Excahnge
surface/boundary, linking
two systems
Skin
Effective barrier:
forms thick,
continous layer
Cut or abrasion - easier entry
Common entry for pathogenic
microorganisms, due to some
adaptations: thin, moist, sticky,
large surface area, well
supplied with blood vessels
Gas-exchange system
Digestive system
Adaptations: Thick mucous
layer that covers exchange
surfaces and forms a thick,
sticky barrier, hard to
penetrate - Production of
enzymes, - production of
stomach acid.
Chemical
Breaks down large, insoluble
molecules, into smaller, soluble ones
Uses enzymes, called
hydrolases
Hydrolysis is the
splitting up of molcules
by the addition of water
Examples of hydrolases:
Carbohydrases, lipases,
proteases.
Assimilation - the incorporation of
molecules into body tissues
Absorption - taking soluble
molecules into the body
Physical
Break down of large pieces of food into
smaller ones by the means of structures,
such as teeth
Makes it possible to
ingest food
Provides a large surface
area for chemical
digestion