Welcome to My AP Biology Thoughts podcast, my name is Jacqueline Sun and I am your host for episode 85 called Unit 4 Cell Communication and Cell Cycle: The Immune System. Today we will be discussing how your body defends itself against infection and stays healthy through the complex yet vital immune system.

•  The immune system is responsible for fighting off germs and other harmful outside invaders from entering and wreaking havoc on your body
• Different from all other systems in that it is not a specific cell, tissue, or organ but is rather composed of several different cells, tissues, and organs working in tandem.
• There are many important components of the immune system that can be divided into two general categories: the innate (or the non specific defense system), and the adaptive (or the specific defense system).

Innate (Nonspecific defense system). As the name suggests, you are born with it and it is automatically activated in the face of threats.

• Uses physical and chemical barriers, killer cells, and fevers to defend the body
• Simple Physical Barrier is the first aspect of the innate immune system
• The skin is the first line of defense. It covers nearly every part of your outside body and acts as a physical barrier and keeps out many harmful microorganisms. As long as the skin is mostly undamaged or unharmed, its defense will hold.
• Mucous membranes also provide a physical barrier. They line the body cavities that connect the inside of your body to the outside, such as the respiratory and urinary system. The thick viscosity of the mucus aids in preventing the entry of harmful microorganisms.
• Both of these physical barriers also provide chemical defense. For example, The skin and stomach can secrete acids to kill off invaders. Sweat, which is also secreted by the skin, has antimicrobial proteins to kill bacteria. Enzymes can be found in mucus that perform the same function.
• So lets say your skin was scraped up. Now your body relies on the second line of internal innate defense.
• Your body may instigate a fever, send out chemical signals calling for defense from body parts, or cause inflammation. These are just a few of the main tactics the body may use, there are many more.

SO HOW DOES YOUR BODY DETECT WHERE THE INJURY IS AND WHERE TO DEFEND ITSELF. IT uses the...

• Inflammatory response: A bodily process that uses chemicals to signal to the immune system defenders where the damage to the body is.
• Utilizes redness, swelling, heat, and pain as signal...