Our Body's Defences to Infection

Explains the different barriers to pathogen.

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  • Created by: Megz
  • Created on: 23-12-10 20:20
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Epithelial Defences
Skin has an impenetrable layer toughened by
keratin (fibrous structural protein).
Sebum is an additional oily substance that
contains chemicals which inhibits growth of
microbes but doesn't harm natural skin flora.
The skin flora has an important role in
preventing disease by competing for position
and producing substances inhibiting other
microorganism growth.
Mucus also lines the epithelial layers in our body
which is a sticky substance; traps microbes.
This substance contains lysozymes (enzyme
capable of destroying microbial cell walls).
Lysozymes are present in tears that keep eyes
moist and protect entry of pathogens.
Phagocytic white blood cells engulf and digest
pathogens that may be found on epithelial
Skin defences may be breached if one cuts themselves
as microbes can enter direct through the blood. The
first response would be to seal the wound by blood
clotting- cascade of events involving fibrinogen,
thrombin, platelets and red blood cells.
Gut Defences- Important in fighting against
pathogens. Saliva in the mouth destroys some
bacteria or slows down growth. Acid in the
stomach; HCl with a pH of 2 effectively destroys
majority of ingested microorganisms. Another way
the stomach helps is by contracting which causes
the person to vomit. This discharges the contents
that are harmful.


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