Content originally from the web address: http://www.thehumanbody.ecsd.net/immune_system.htm (I edited this content very little, because it was great to begin with. I was sad to have seen that the site was down. Last checked 9-27-2011)
The Immune System: The Defenders
by Emmett Underhill
The main job of the immune system is to protect our body from foreign invaders. The immune system does this by sending out different types of cells that kill germs.
What are germs?
Germs are bacteria, fungi, parasites, or viruses that make us sick. The cells of the immune system can usually protect us from them.
These are germs:
How do the immune system cells protect us?
1. Special cells called neutrophils and macrophages can eat and destroy germs.
This is called Phagocytosis.
In this picture, a large Macropyhage cell on top, comes down and surrounds and then starts to eat two germ cells.
2. Special cells called lymphocytes can attach to and kills virus infected cells. In this picture, the smaller lymphocyte on the bottom is killing the bigger cell.
What does the immune system look like?
These cells are produced in our bone marrow, thymus, and spleen and circulate in our blood stream looking for invaders.
- Cell Wars by Dr. Fran Balkwill & Mic Rolph published in 1991 by HarperCollins Pulbishers
- The Magic School Bus – Inside Ralphie