Causes of Disease
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Transcript Causes of Disease
Causes of Disease
Chapter 16
Section 1
Objectives
Identify five common types of pathogen
Describe three ways infectious disseases
are spread
Distinguish between infectious diseases
and communicable diseases
Identify two causes of non-infectious
diseases
Key Terms
Pathogen
Infectious disease
Infection
Toxin
Communicable disease
AIDS
HIV
Infectious Diseases
•
•
•
Caused by a pathogen
The pathogen invades the body and
begins to reproduce
There are five important pathogens
– Bacteria
– Protozoa
– Fungi
– Worms
– Viruses
Bacteria
Simple single celled organisms
They live everywhere
◦ On every surface
◦ Including the inside and outside of your body
They are microscopic
◦ Cannot be seen without “help”
Some are harmful, but some are helpful
◦ Toxins result from harmful bacteria
Protozoa
Single celled organisms
Microscopic, but larger than bacteria
Found in most water supplies
◦ Not bottled or filtered water
◦ Most are not dangerous
Fungi
Molds and mushrooms are the most
common examples of Fungi
Many are beneficial to humans
Some are pathogens
◦ Athlete’s Foot
◦ Ringworm
◦ Thrush
Worms
Worms can enter the body in a variety of
ways
They are usually immature when they enter
They move to specific tissues or organs as
they mature
Pathogenic worms
◦ From the environment
Hookworms from the soil
◦ From food
Trichina from raw or undercooked meats
Viruses
Much smaller that most bacteria
A virus is not a cell based organism
◦ It is made of a protein coat
◦ It contains a type of genetic material
They only reproduce inside other cells
◦ It takes over the cell
◦ Destroys the cell
◦ Infects nearby cells
More about Infectious Disease
The ability of one person or organism to
transfer the infection to another person
or organism describes a communicable
disease
Some diseases do not transfer well from
one individual to another
A highly infectious disease may stay in one
kind of organism
◦ “bird flu” found in poultry
◦ Not HIV, found in several types of organism
AIDS
AIDS is a communicable disease caused
by a virus
AIDS is caused by HIV
It is possible to test for AIDS
There are treatments, but as yet no cure
for AIDS
See page 522, Table 16.1 to see methods of disease transmission
Non-Infectious Diseases
NOT caused by pathogens
NOT communicable
These diseases may be inherited
◦ Muscular dystrophy, sickle cell anemia, cancer
These diseases may be caused by the
environment or exposure to toxins
◦ Cancer, heart diseases, arthritis
Summary
Infectious diseases are caused by pathogens
◦ Bacteria, protozoa, fungi, worms, and viruses
Pathogens invade the body, reproduce,
causing an infection
Communicable diseases are infectious
diseases that can be spread from person to
person
Non-infectious diseases are NOT caused by
pathogens, but by genetic factors, the
environment, or both
Definitions
Pathogen is a virus or microorganism that
causes disease
Infectious disease is an illness caused by a
pathogen
Infection is the invasion and multiplication
of pathogens in the body
Toxin is a poisonous substance
Definitions
Communicable disease is an infection that
can be spread from person to person
AIDS, (acquired immuno-deficiency
syndrome) is a viral disease that destroys
the body’s ability to resist other diseases
by disrupting the immune system
HIV, human immuno-deficiency virus) is
the virus that causes AIDS