Aim: How does our body defend us from pathogens?

Pathogens Any disease-producing agent! Examples: virus, bacterium, fungus, or parasite.

1st Line of Defense Skin Mucus Tears in eyes Acid in stomach Show an apple and discuss the skin’s job.

How do these things help to protect us? Tears and sweat: has enzymes that are able to destroy pathogens . stomach has HCL to kill bacteria. Hair and mucus trap potential disease causing pathogens.

2nd Line of Defense The Immune System

Cellular Components: White Blood cells Large cells with a nucleus. Defenders of the body. Two Types of white blood cells: Phagocytes: engulf and destroy bacteria Lymphocytes: produce antibodies

Immune System Made of proteins, cells, and tissues that identify and defend the body against foreign chemicals and organisms

How does our immune system identify foreign cells? They are proteins on our cells (like an ID tag) Antigen IF the ID tag identifies the invader as not belonging to the body (non-self), then the ID tag is called an antigen.

If the Antigen is foreign….. What will the immune system do? ATTACK IT!!!!

Phagocytes – Engulf the Pathogens

Lymphocytes:Produce antibodies They can make antibodies, which are their weapons against the foreign antigens. Very specific, only one antibody will fight only a certain antigen! Antibodies & Antigens are both proteins!!

Antibodies They are weapons that fight against pathogens Pathogen Use screw motivation Antigens

How are nuts and screws similar to antigens and antibodies? Antibodies are made specifically to match the shape of the antigen. 1 antigen = 1 antibody What does this remind you of? Do screw and nut motivation

How do antibodies destroy pathogens? When the antibody attaches to the antigen, it breaks open its cell membrane Or, the antibody attaches to the antigen, and a phagocyte will know to engulf it Balloon and pin motivation

Our Immune System has a good memory! The first response is relatively slow and weak because time is needed for enough WBCs to form and defeat the pathogen. The second response to the same pathogen triggers a quicker and stronger response. ** After the first response, the immune system “remembers ”specific pathogens by leaving behind specific WBCs that protect the body for years (memory cells).