Immune System

1. Immune System

2. Purpose: • It is designed to defend against millions of bacteria, microbes, viruses, toxins and parasites that would love to invade your body. • It works around the clock in thousands of different ways, but it does its work largely unnoticed. One thing that causes us to really notice our immune system is when it fails for some reason. We also notice it when it does somethingthat has a side effect we can see or feel.

3. Examples of Immune System side effects • When you get a cut, all sorts of bacteria and viruses enter your body through the break in the skin. Your immune system responds and eliminates the invaders while the skin heals itself and seals the puncture. In rare cases the immune system misses something and the cut gets infected. It gets inflamed and will often fill with pus. Inflammation and pus are both side-effects of the immune system doing its job. • When a mosquito bites you, you get a red, itchy bump. • Each day you inhale thousands of germs (bacteria and viruses) that are floating in the air. Your immune system deals with all of them without a problem. Occasionally a germ gets past the immune system and you catch a cold, get the flu or worse. A cold or flu is a visible sign that your immune system failed to stop the germ. • Each day you also eat hundreds of germs, and again most of these die in the saliva or the acid of the stomach. Occasionally, however, one gets through and causes food poisoning. • Allergies are really just the immune system overreacting to certain stimuli that other people don't react to at all.

4. Components of the Immune System • Skin • Thymus • Spleen • Lymph system • Bone marrow • White blood cells

5. Skin • The body’s first line of defense. It acts as a primary boundary between germs and your body. • Skin is tough and generally impermeable to bacteria and viruses. • The skin also secretes antibacterial substances. These substances explain why you don't wake up in the morning with a layer of mold growing on your skin -- most bacteria and spores that land on the skin die quickly.

6. Thymus • Located between your breast bone and your heart. • Responsible for producing T-cells and is especially important in newborn babies - without a thymus a baby's immune system collapses and the baby will die.

7. Spleen • Filters the blood looking for foreign cells (the spleen is also looking for old red blood cells in need of replacement). • A person missing their spleen gets sick much more often than someone with a spleen. • The spleen is located in the upper left quadrant of the abdomen.

8. Lymph Nodes • Small, bean-shaped structures • Help restore fluid lost by the blood and return it to the circulatory system

9. Bone Marrow • The soft, spongy tissue found in bone cavities. • Produces new blood cells, both red and white. • Red blood cells are fully formed in the marrow and then enter the bloodstream. • White blood cells mature elsewhere.

10. White Blood Cells • The white blood cells are probably the most important part of your immune system. • "white blood cells" are actually a whole collection of different cells that work together to destroy bacteria and viruses.

11. Disorders of the Immune System: Autoimmune Disease • Sometimes the immune system's recognition apparatus breaks down, and the body begins to manufacture antibodies and T cells directed against the body's own cells and organs. • Cancer • AIDS The electron microscope picture is a macrophage (large, orange) attacking germs (small, green).   The macrophage is a general purpose antibody -- it eats any type of bug!