1. Immune system

2. If a pathogen gets through the first two lines of defense
Third line of defense takes over

3. What is the Immune System
The body system that fights to protect the body from specific pathogens
Immune response special response to each type of pathogen
Carries lymph
Yellowish liquid that are normally between cells in tissues

4. Organs of the Immune System
Bone Marrow  produces white blood cells
Lymphocytes
Thymus Gland  stores lymphocytes while they mature
Spleen  filters pathogens out of the blood
Tonsils trap pathogens that enter the body through the mouth

5. Circulation of Lymph
Lymph vessels act similarly to the circulatory system, but they only circulate lymph
Muscles around the vessels contract and relax to circulate the lymph throughout the body  heart does not pump lymph
Prior to entering the blood stream via both Vena Cavas the lymph gets through the nodes (filters)

6. lymphocytes
Type of white blood cell involved in an immune system response
2 main types T and B cells
Named after their location of maturity
T cells Mature in Thymus Gland
B Cells  Mature in Bone Marrow
Both have specific defense mechanisms

7. Immune Responses B-Cells
B cells respond to pathogens in the blood and lymph
Make Antibodies that bind to antigens
Once they bind together it signals a phagocyte to engulf and destroy it

8. Immune Response T-Cells
Killer T-cells destroy infected, damaged, or cancerous body cells
Releases toxins when the cell comes into contact infected cell
Toxin makes holes in infected cell and causes the cell to burst open

9. Immune system helper t-cells
Helper T-cells release chemicals that control other lymphocytes
These chemicals turn on the Kill T-cells and B-cells

10. Immunity and Vaccination
Most B and T cells dies after the infection has been brought under control
The ones that do not die become Memory Cells
Helps the immune system remember a pathogen
Helps to fight the pathogen if it enters the body again
Why vaccinate?
The process of exposing a person to pathogens on purpose so the individual will develop immunity to them
Only part, weakened, or dead version of the pathogen are injected