Transcript Chapter 12 - Cloudfront.net

Chapter 22
Disease and the Body’s Immune
System
Disease
• A disease is any condition which interferes
with the normal functioning of the body.
• Scientists refer to any organism which
causes disease as a pathogen.
• Pathogens include microscopic creatures
such as bacteria, fungi, protozoans, and
viruses…even some larger creatures like
parasitic worms…
The Fight Against Disease
• Before 1870, one third of children died
before adulthood…
• Now, with preventive drugs and treatment,
less than one in one hundred die…
• Emphasis on the fight against disease has
changed to adults…who are now living
longer and longer lives…
Classification of Diseases
• Diseases are classified as
infectious (caused by a pathogen)
noninfectious (caused by other factors
– aging, genetic, poor nutrition and others)
• Both of these can be classified as
acute (severe but lasting only a short
time)
chronic (long-lasting or often occurring)
Types of Infectious Diseases
• Infectious diseases may be further classified as
communicable (transferred from person to
person)
noncommunicable (not transferred from
person to person)
Example: colds – passed from person to person
tetanus – not passed from person to
person
Noninfectious Diseases
Types of noninfectious diseases
1. Degenerative Diseases – organs
gradually lose their ability to function
properly over time…
Examples: Heart disease,
Alzheimer’s, Parkinson’s, osteoporosis
Noninfectious Diseases
2. Immunological diseases – The immune
system malfunctions and overreacts to a
foreign material, attack the body, or fail to
function properly.
Most common: Allergies
Most severe: autoimmune diseases
(body attacks itself)
Example: rheumatoid arthritis,
and lupus
Noninfectious Diseases
3. Hormonal Diseases – malfunctions of the
endocrine system
Example: Diabetes
4. Congenital Diseases – Present at birth
Sometimes referred to as birth defects
Many are inherited – hemophilia, sickle-cell
anemia
Some are infectious – passed from mother to
baby
Many are genetic – Down’s syndrome
Noninfectious Diseases
5. Psychosomatic Diseases – caused by the
mind
6. Nutritional Diseases – caused by
improper diet
results in a deficiency disease caused
by malnutrition
Example: scurvy, rickets, anemia
Noninfectious Diseases
7. Diseases caused by harmful substances
Infectious Disease
• Organisms responsible for disease:
1. bacteria
2. viruses
3. protozoans
4. fungus’ – myotic diseases
5. worms – helminthic diseases
The Bacteria
• Single celled organisms
• They are a prokaryotic cell – lack a
membrane bound nucleus
• Varying structures:
– Most have a cell wall
– Some have a slimy outer layer
– Some have capsules
– Some have flagella allowing them to move
The Bacteria
• Basic bacterial shapes – there are three
basic shapes:
– Cocci – round shape (tiny spheres)
– Bacilli – rod shaped
– Spirilla – spiral shaped
The Bacteria
• Examples of pathogenic cocci:
– Staphylococcus aureus: this causes staph
infections
– Streptococcus pneumonia: causes bacterial
pneumonia
– Streptococcus pyogenes: causes “strep
throat”
The Bacteria
• Examples of pathogenic bacilli:
– Mycobacterium – leprosy and tuberculosis
– Salmonella – food poisoning and typhoid
fever
– Escherichia coli – food poisoning
The Bacteria
• Examples of spirilla that are pathogenic:
– Syphilis
– Lyme disease
Heterotrophic and Autotrophic
Bacteria
• Autotrophic means it is a “self feeder” – it
produces its own food…
• They contain chlorophyll…
• Heterotrophic means it needs an outside
source for food…
• Some heterotrophic bacteria are extremely
harmful…
• Some are helpful, they assist your body in
its maintenance…like E. coli…
Reproduction of Bacteria
• They produce asexually by binary fission..
• One cell splits into two…
• Sometimes, some bacteria does exchange
DNA before splitting…
Bacteria and Disease
• Pasteur’s germ concept of disease…
– He said that every infectious disease is
caused by a specific germ.
Pathogenic activities of bacteria
• Pathogenic bacteria cause problems in several
ways…
• They steal a cell’s nutrients – vitamins and
minerals
• Many produce harmful substances – toxins that
damage or kill infected cells of the individual.
• Turn the bodies tissues into battlegrounds…cells
near the infected area are often killed between
the battle of the immune system and the
bacteria.
Viruses
• What is a virus?
– A virus is a tiny capsule of genetic
information.
– It is a genetic “program” that reprograms the
machinery of a living cell to produce a new
virus particle instead of a cell’s normal
products.
Viruses
• Structure:
– Unlike living cells, a virus consists of only a
short string of DNA or RNA surrounded by a
rigid structure called a capsule…
– Some viruses also have a lipid envelope…
Viruses
• Replication:
– New viruses are manufactured and
assembled by infected cells…
– The cells own factories build new viruses after
the virus changes the DNA code of that cell…
– A typical virus is essentially a capsule of
“blueprints” for new viruses…
– Because a virus is incapable of reproducing
on its own, virologists are uncertain whether
or not to classify viruses as living things…
Protozoa
• Diseases caused by protozoa:
– Single celled animals
– Malaria is an example – caused by the
organism Plasmodium – it is common in
tropical regions…
– 150 million new cases occur each year…
– Other diseases: amoebic dysentery, African
sleeping sickness…
Fungi
• Fungal diseases are called “mycotic
diseases”
• Examples: Athlete’s foot and ringworm
• Most cases of dandruff are fungal
• Most fungal diseases are characterized by
red, inflamed, flaking skin…
Roundworms, Tapeworms, Flukes
• The body can be invaded by parasitic
worms..
• Examples of Diseases: trichinosis &
hookworm
Spread of Infectious Diseases
• Modes of transmission:
– Droplet transmission – saliva (sneezes)
– Droplet is the most common form of
transmission
– A person can be a carrier and display no sign
of disease…
– Disease can be transferred by a vector…like
a mosquito…
– Some diseases are transferred by
contaminated substances…
Spread of Infectious Disease
• Venereal Diseases:
– Diseases that are spread through sexual
contact…
– STD’s is what they are referred to today…
– In 1995, it was estimated that 1 in six
teenagers had an STD…
Spread of Infectious Disease
• Incubation and infection:
– A person is said to have an infection the
moment the pathogen enters the body…
– There is an interval of time from the initial
infection and the sign of disease…this is
called the incubation period…
Preventing Disease
• Wash your hands!!!
• God instructed the Israelites to wash after
touching any possible infectious object…
• Avoid unnecessary contact…
• Avoid the contamination…
• Eliminate vectors…
• Vaccinations
The Immune System
• The most important parts of the immune
system are the white blood cells…
• They search out and destroy any organism
or substance they do not recognize…
• They are assisted by the lymphatic
system…which transports white blood
cells around the body and cleans the fluids
of pathogens…
The End