1. The Immune System

2. Parts of the Immune System
Skin, hair, mucus, and acids are first-line defenses which help keep germs from reaching the parts of your body where they can make you sick.
Your skin keeps dirt and germs from entering your body.
Sweat and acids from skin cells kill some bacteria, and natural oils make skin waterproof so you can easily wash it.

3. Parts of the Immune System (cont.)
Hairs in your nose and hairlike structures called cilia trap pathogens in the upper respiratory system and move them out of your body.
The digestive system is effective at stopping pathogens that enter your body on or in the food you eat.

4. Parts of the Immune System (cont.)
Stomach acids destroy many pathogens.
Pathogens can be moved through the circulatory system to organs that fight infections.
The nervous and circulatory systems work together to produce a fever.
The high temperature kills many pathogens and stimulates white blood cell production.

5. Parts of the Immune System (cont.)
White blood cells and inflammatory response make up your body’s second-line defenses.
Some white blood cells surround and destroy bacteria directly and others release chemicals that make it easier to kill the pathogens.
Another type of white blood cell produces proteins that destroy viruses and other foreign substances.

6. Parts of the Immune System (cont.)
Inflammation is a process that causes the area around an injury to become red and swollen.

7. Parts of the Immune System (cont.)
The inflammatory response cleans the area of the injury and keeps the infection from spreading, enabling the damaged tissue to heal.

9. Parts of the Immune System (cont.)
Third-line defenses are specific to foreign substances.
An antigen is a substance that causes an immune response.
Proteins called antibodies can attach to the antigen and make it useless.
Certain white blood cells, called B cells and T cells, form antibodies.

10. Parts of the Immune System (cont.)
B cells form and mature in the bone marrow and secrete antibodies into the blood.
T cells form in the bone marrow and mature in the thymus gland, producing a protein antibody that becomes part of a cell membrane.
Antibodies match with specific antigens.