body defences

8/7/2019 Body defences

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Body Defenses

By Bridgette Davies



� Pathogens and

microorganisms are the two

main types of pathogen.

Bacteria releases toxins andviruses damage our cells.

White blood cells can ingest

and destroy pathogens. They

can also produce antibodies

to destroy pathogens.

Antitoxins neutralise toxins.



BacteriaBacteria are microscopic organisms. They come in many

shapes and sizes.

Bacteria are living cells and can multiply rapidly. When in

the body they release poisons or toxins that make us feel

ill. The diseases caused by bacteria include:� Food poisoning

� Cholera

� Typhoid

� Whooping cough

� Gonorrhoea (a sexually transmitted disease)

Bacteria can grow in soil, acidic hot springs, radioactive

waste, water, and deep in the earths crust.



Disease or Virus?Pathogens - viruses

Viruses are very much smaller than bacteria. They are along

with the smallest organisms recognized and consist of a

part of genetic material.

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 fillthe 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:

� influenza - flu

� colds

� measles

� mumps

� rubella

� chicken pox

� AIDS



White Blood CellsWhite blood cells

Functions of the white blood cells

A white blood cell ingesting disease-causing bacteria

White blood cells can:

ingest pathogens and destroy them

produce antibodies to destroy pathogens

produce antitoxins that neutralise the toxins releasedby pathogens

In a written examination, it is easy to get carried away and

waffle on about things such as invaders and battles,

but stick to the point. Note that:

the pathogens are not the disease ± they cause the

diseasewhite blood cells do not eat the pathogens ± they

ingest them

antibodies and antitoxins are not living things ± they

are specialised proteins



� Antibiotics

� Antibiotics are substances that kill bacteria or stop their growth. They do not work

against viruses: it is difficult to develop drugs that kill viruses without also damagingthe body¶s tissues.

� How some common antibiotics work

�antibiotic how it works penicillin breaks down cell walls erythromycin in stopsprotein synthesisneomycinstops protein synthesisvancomycinstops protein

synthesisciprofloxacin stops DNA replication Penicillin

�

� A bacterium damaged and distorted by penicillin

� The first antibiotic - penicillin - was discovered in 1928 by Alexander Fleming. He

noticed that some bacteria he had left in a petri dish had been killed by naturallyoccurring penicillium mould.

� Since the discovery of penicillin, many other antibiotics have been discovered or

developed. Most antibiotics used in medicine have been altered chemically to makethem more effective and safer for humans.

� Resistance

� Bacterial strains can develop resistance to antibiotics. This happens because of naturalselection. In a large population of bacteria, there may be some cells that are notaffected by the antibiotic. These cells survive and reproduce, producing even morebacteria that are not affected by the antibiotic.

� MRSA is methicillin-resistant staphylococcus aureus. It is very dangerous because it is

resistant to most antibiotics. It is important to avoid over-use of antibiotics, so we canslow down, or stop, the development of other strains of resistant bacteria.

� 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 wereignored at the time because people did not know that diseases were caused bypathogens that could be killed.



White blood cells

The white blood cells

have a rather shortlife cycle, living froma few days to a fewweeks. A drop of blood can containanywhere from 7,000to 25,000 white bloodcells at a time. If an

invading infectionfights back andpersists, that numberwill significantly

increase.



Blood Vessels

� The blood vessels are the part of the

circulatory system that transport blood

throughout the body. There are three

major types of blood vessels: the arteries,

which carry the blood away from the heart;

the capillaries, which enable the actual

exchange of water and chemicals betweenthe blood and the tissues; and the veins,

which carry blood from the capillaries back

toward the heart.



The immune system

� The immune system is composed of many interdependent cell typesthat collectively protect the body from bacterial, parasitic, fungal,viral infections and from the growth of tumor cells. Many of these celltypes have specialized functions. The cells of the immune systemcan engulf bacteria, kill parasites or tumor cells, or kill viral-infectedcells. Often, these cells depend on the T helper subset for activationsignals in the form of secretions formally known as cytokines,lymphokines, or more specifically interleukins. The purpose of thisarticle is to review the organs, cell types and interactions betweencells of the immune system as a commentary on their importanceand interdependence on the T helper subset. Such anunderstanding may help comprehend the root of immune

deficiencies, and perceive potential avenues that the immunesystem can be modulated in the case of specific diseases.



Smallpox



Medicine



Medicine timeline



Glossary!



� the bodys defense system is the imune system and uhave white blood cells that fight viruses and remove thequanity but if you get food poisining your body will throwup until it is gone

� The defense system is related to the immune system.Removing unwanted substances is a job to the liver andkidneys. But they can't remove or expel any quantity of unwanted substances. If the amount is high, the bodymay become seriously intoxicated and needs medical

aid. Our skin also help the body to remove substancesthrough sweat. The immunologic system attacksdangerous invaders with specialized white blooddefenders called leukocites and others.

body defences

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