The Body’s Defenses

California Standards 10.a., b. & c.

Pathogens• Pathogens are disease causing agents

such as:1. bacteria2. viruses3. prions and4. single cell organisms

First Line of Defense

1. Skin: prevents pathogens from entering the body

Skin = the first line of defense

The skin is the organ which defends the body

from infection by blocking the entry of pathogens.

2. Mucous Membranes: found in your nose and throat and stop the entry of pathogens into your body.

Second Line of Defense

1. Inflammatory Response

2. Temperature Response

3. Proteins

4. White Blood Cells

1.Inflammatory Response

• A series of events that suppress infection and speed recovery

• Histamine: increase blood flow by dilating blood vessels.

• White blood cells invade infected area

• Swelling and redness occurs

When the skin is punctured pathogens are allowed to enter the body.Pathogens

capillary

Injured or damaged cells release the

chemical histamine which causes the blood vessels to dilate increasing blood flow to the

area. This blood flow causes swelling and redness to the area.

Increased blood flow bring white blood cells that attack and destroy pathogens. The presence of ‘puss’ at a wound is the presence of white blood cells.

2. Temperature Response

• 1. Higher temperature called a fever

• 2. Bacteria do not grow well at high temperatures

• 3. Enzymes are destroyed or denatured

Temperature Response

Basically, the temperature is a response that is helpful in

fighting pathogens because bacteria do not grow well at

high temperatures.

Bacteria and Antibiotics

Antibiotics are specifically used to kill bacterial infections. They do nothing for viral, or virus caused, infections.

3. Proteins• 1. Complementary System made

up of 20 different proteins.

• 2. Punctures cell membrane of bacteria

• 3. Interferon released to fight viruses

4. White Blood Cells

• Neutrophils

• Macrophages

• Natural Killer Cells

Neutrophils

• Engulf and destroy pathogens

• Release chemicals that kill bacteria and themselves

Macrophages

• Kill and ingest pathogens

• Clear dead cells and other debris

• Found in spleen and lungs

Natural Killer Cells

• Attacks cells infected with pathogens

• Puncture cell membrane

• Detect and kill cancer cells

• Skin• Mucous membranes• Inflammatory response• Temperature• Protein• White blood cells

Nonspecific Defense:

Third Line of Defense

Specific Defense Against Disease

The last type of defense against invading

organisms is the specific line of defense. This defense by your body attacks specific

pathogens and in the process produces antibodies that in the future can attack that

specific pathogen if it occurs again.

Third Line of Defense• Immune Response: consists of an army

of cells that combat specific pathogens

• Antigen: a substance that triggers an immune response

• Antibody: a ‘Y-shaped molecule that is produced by plasma cells when exposed to an antigen.

Non-functioning immune response

A person’s immune response is not functioning well if it is unable to fight pathogens. This is because their body cannot produce the specific antibody for that pathogen. AIDS is just such a disease because a patient’s body inability to defend itself against invading organisms.

Antibodies and Antigens• An antibody is produced by your

body in response to a specific antigen.

• An antigen is a foreign substance which causes the body to produce a specific antibody.

Antibodies attacking an antigen

‘Y’ shaped antibody

Antibodies

Antibodies are substances formed by the human body in response to

foreign proteins entering the body.

Resistance to Disease

• Immunity – resistance to a particular disease.

• Vaccination – a medical procedure used to produce immunity.

• Vaccine – a solution of dead or modified pathogens that can no longer cause disease.

Vaccines and Infection

Vaccines are effective in preventing disease because they are dead or modified pathogens

with antibodies directed against a specific pathogen.

The End