Defending Against Infection

Defending Against Infection Lots on: Pathogens, Disease, Antibiotics, Penicillen, Bacteria and Viruses.

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  • Created on: 26-03-10 17:11
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Defending against infection.
Pathogens are microorganisms such as bacteria and viruses that
cause disease. Bacteria release toxins, and viruses damage our cells.
White blood cells can ingest and destroy pathogens. They can produce
antibodies to destroy pathogens, and antitoxins to neutralise toxins.
In vaccination pathogens are introduced into the body in a weakened
form. The process causes the body to produce enough white blood cells
to protect itself against the pathogens, while not getting diseased.
Antibiotics are effective against bacteria, but not against viruses. Some
strains of bacteria are resistant to antibiotics.
Pathogens bacteria
Pathogens are microorganisms that cause infectious disease. Bacteria
and viruses are the main pathogens.
Bacteria.
Bacteria are microscopic organisms. They come in many shapes and
sizes, but even the largest are only 10 micrometres long 10 millionths
of a metre.
Bacteria are living cells and, in favourable conditions, can multiply
rapidly. Once inside the body, they release poisons or toxins that make
us feel ill. Diseases caused by bacteria include:
1.food poisoning.
2.cholera.
3.typhoid.
4.whooping cough.
5.gonorrhoea a sexually transmitted disease.
Pathogens ­ viruses
Viruses are many times smaller than bacteria. They are among the
smallest organisms known and consist of a fragment of genetic material
inside a protective protein coat.
Viruses can only reproduce inside host cells, and they damage the cell
when they do this. A virus can get inside a cell and, once there, take over
and make hundreds of thousands of copies of itself. Eventually the virus
copies fill the whole host cell and burst it open. The viruses are then
passed out in the bloodstream, the airways, or by other routes.
Diseases caused by viruses include:

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­ flu.
2.colds.
3.measles.
4.mumps.
5.rubella.
6.chicken pox.
7.AIDS.
White blood cells.
The body has different ways of protecting itself against pathogens. The
first defence is passive immunity. This is aimed at stopping the pathogen
getting into the body in the first place. The body's passive immunity
system includes the skin, mucus and cilia in the respiratory system, acid
in the stomach, and enzymes in tears.
If a pathogen still manages to get into the body, the second defence
takes over.…read more

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More about white blood cells
There are several different types of white blood cells, each with different
functions, but they can be put into two main groups:
1.phagocytes or macrophages.
2.lymphocytes.
Phagocytes
Phagocytes can easily pass through blood vessel walls into the
surrounding tissue and move towards pathogens or toxins. They then
either:
1.ingest and absorb the pathogens or toxins.
2.release an enzyme to destroy them.…read more

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Vaccination involves putting a small amount of an inactive form of a
pathogen, or dead pathogen, into the body. Vaccines can contain:
1.live pathogens treated to make them harmless.
2.harmless fragments of the pathogen.
3. toxins produced by pathogens.
4. dead pathogens.
These all act as antigens. When injected into the body, they stimulate
white blood cells to produce antibodies against the pathogen.…read more

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Cleanliness.One simple way to reduce the risk of infection is to maintain
personal hygiene and to keep hospitals clean. In the 19th century, Ignaz
Semmelweis realised the importance of cleanliness in hospitals. However,
although his ideas were successful, they were ignored at the time
because people did not know that diseases were caused by pathogens
that could be killed.…read more

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