Download Pathogen – a biological agent of disease that infects its host with a

Define the term pathogen.
Pathogen – a biological agent of disease that infects its host with a virus, bacterial
infection, or fungi
Outline the role of the skin and mucous membranes in defence against pathogens.
The role of skin in defense against pathogens:
 Skin is continually producing new skin cells to replace the dead cells, and if kept
unbroken, it will prevent pathogens from entering. The pores in the skin contain
substances such as acids and wastes, as well as salt that is naturally in our body
that effectively kill bacteria.
The role of mucus membranes in defense against pathogens:
 Mucus membranes are located in the respiratory tracts and reproductive systems,
and because it is so thick and sticky it traps and keeps the pathogens away from
body parts harmful of infection. As more pathogens enter, more mucus is
produced. That’s why a person with a cold often has more mucus in their throat
than a normal person. Mucus is expelled from the body through, for example,
sneezing.
Places in which mucus membranes occur
Outline how phagocytic leucocytes ingest pathogens in the blood and in body tissues.
If a microorganism gets past the nonspecific defense system of the body, then they will
be recognized as a foreign object by the proteins on their surface. When they are
recognized a secondary immune response is triggered. One part of this is the ingestion of
the antigen by phagocytes (a type of leukocyte) using endocytosis. During endocytosis,
once the pathogen is killed, they are digested by the lysosomes inside the phagocyte.
Phagocytes can complete this process inside tissue or in the blood as they can squeeze
through blood capillaries. Large numbers or phagocytes at a site of infection form pus.
A simplified picture of endocytosis.
Describe the process of blood clotting
To stop blood loss when blood vessels are broken, the
body uses the mechanism of blood clotting.
This process is made up of four main steps.
The first is that the damaged cells release into plasma
at the site of the cut clotting factors, a group of
proteins.
The inactive enzyme prothrombin is activated into
thrombin by the clotting factors.
The thrombin turns the soluble plasma protein
fibrinogen into its fibrous fibrin, which is insoluble.
Finally, fibrin connects platelets and erythrocytes to form a clot which stops blood flow
from the cut.
.
Sources:
Charles Stuart university. "HSC Online." NSW HSC Online. 2 Oct. 2009
<http://www.hsc.csu.edu.au/biology/core/better_health/9_4_4/944net.html>.
"Phagocytosis." Wikipedia, the free encyclopedia. 22 June 2009. 7 Oct. 2009
<http://en.wikipedia.org/wiki/File:Phagocytosis2.png>.
"Topic 11.1 Defence against infectious disease." Click4Biology. 2 Oct. 2009
<http://click4biology.info/c4b/11/hum11.1.htm#1>.