Immune System - Cloudfront.net
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Immune System
AND INFECTIOUS DISEASES
Immune System
The network of cells, tissues,
and organs that work together
to protect the body against
infectious invaders.
The organs involved in the
immune system are called the
lymphatic system and consist of:
Thymus
Spleen
Bone Marrow
Lymph Nodes
These are important parts of the
immune system because they
produce or store leukocytes
Leukocytes
Leukocytes circulate through the blood and lymphatic system
and there are two types:
Phagocytes
Cells that engulf and break
down the invading organism
Most common is neutrophils,
which fight bacteria
Lymphocytes
cells that allow the body
to remember and
recognize previous
invaders and help the
body destroy them
B-cells and T-cells find
organisms identified by
antibodies and destroys
them
Lymphocyte Response
When foreign organisms (antigens) are recognized by the body
B-cells produce antibodies
Antibodies are proteins that are developed to lock onto specific
antigens
These antibodies will be present in your body for life, so the next
time that antigen enters your body it is destroyed very quickly
That is how immunizations work, they introduce a weakened
antigen into your body, so your body
can produce antibodies in case a
stronger antigen returns
Antibodies cannot destroy these
antigens on their own, the T-cells
destroy the antigens
Types of Immunity
Humans have three different types of immunity:
Innate – immunity you are born with
Adaptive – immunity that develops throughout our lives
Passive – immunity that is borrowed from another person or
source
Innate Immunity
This includes lots of our external
barriers that prevent antigens from
ever entering our bodies
Our skin prevent germs from entering our blood stream
If there is a break in the skin, it will try to heal and blood flows
outward preventing the infection from getting inside
Our breathing passages are covered in hairs and mucus that
are meant to trap foreign organisms and expel them from our
bodies
Organisms that enter through our mouth will either be killed
by the chemicals in our saliva or the acid in our stomach
Adaptive Immunity
Adaptive immunity includes the
antibodies we develop by being
exposed to different diseases
throughout our lives and the
vaccinations we receive
Passive Immunity
Sometimes we can borrow immunity from another
source, but this does not usually last for very long
The most common example of this is when babies get
antibodies from the mother’s breast milk, which is
one reason breast feeding is beneficial for babies
Milk really does a body good
(breast milk)
Inflammatory Response
Inflammatory response is when fluid and white blood cells
leak out of the blood vessels and into the tissues.
The white blood cells fight the pathogens
During an inflammatory response, the blood vessel get
wider to increase the flow of blood to that area
Because of the increase blood flow and the fluid leaking
into the tissue, an inflamed area will look red and swollen.
Also, the inflamed area will feel warn to the touch.
In some cases, the inflammatory response will result in you
having a temperature. This high temperature keeps
pathogens from reproducing.
Infectious Diseases
a disease that can be passed from one organism to
another (called antigens or pathogens)
When you have an infectious disease, a pathogen has
gotten into your body and harmed it
Pathogens make you sick by damaging individual
cells
There are four major groups of pathogens
Bacteria
Bacteria are single cell organisms
Bacteria are classified as PROKARYOTES
Most bacteria cannot make their own food; they
have to break down, or decompose, other living
things to obtain their energy
Most bacteria do not cause diseases
Bacteria are almost everywhere:
air, food, water, soil.
Example: Strep throat
Viruses
Virus – a nonliving particle consisting of a core of
hereditary material surrounded by a protein coat.
Viruses can reproduce ONLY inside a living
cell.
Examples: Flu, common cold
Fungi
Most fungi are multicellular
Fungi obtain food by secreting enzymes onto the
dead material outside of their bodies (external
digestion). The fungi then absorb the nutrients
into their cells. Organisms that feed this way are
called SAPROPHYTES
Example: Athlete’s foot
Protists
One cell organisms (unicellular) that have
organelles
Example: Malaria
Man-Made Defenses
PASTERUIZATION – a
heating process that is
used today to kill
microorganisms in food
products such as milk
ANTIBIOTICS – a
chemical that is used to
kill bacteria or slow
their growth without
harming your body cells.
Unfortunately, there is
no way to cure viral
diseases.
Spread of Disease
PERSON-TO-PERSON TRANSFER
Diseases can be transferred by direct contact such as kissing and shaking
hands
Diseases can be transferred by indirect contact such as sneezing and
coughing
CONTAMINATED OBJECTS
Food and water can become contaminated
You can get ill by using contaminated objects such as towels and silverware
ANIMAL BITES
An infected animal can pass on pathogens through their bite
Examples: rabies (dog, raccoon), Lyme disease (tick), malaria (mosquitoes
in tropical areas)
PATHOGENS FROM THE ENVIRONMENT
Some pathogens live naturally in the soil and water
Example: tetanus, botulism (causes food poisoning)
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