But sometimes germs and bacteria get past these outer parts of the immune system. So what are the parts of the immune system that you can not see?

There are many different parts of the immune system inside your body.

One is called the lymph system. The lymph system extends all over inside your body like blood. Lymph is a clear fluid. It brings water and nutrients to the cells in your body. Lymph also finds bacteria in your blood stream. It carries these bacteria to the lymph nodes. The lymph nodes are inside your neck. Often if you are sick you may be able to feel these lymph nodes. They become swollen or larger when they are fighting bacteria and in faction. Another important part of the immune system that you cannot see is your thymus. Your thymus is in your chest. It is between your breast bone and your heart. The thymus produces t-cells.

T-cells can find cells in your body ate carrying viruses. When a t-cell finds a cell with a virus it kills that cell. Your spleen is also an important organ in your immune system. Blood flows through your spleen.

Your spleen looks carefully through your blood for foreign cells. You can live without a spleen. But a person without a spleen will get sick more often than a person with a spleen. There is also an important part of your immune system in your bones! Bone marrow produces new blood cells. There are two kinds of blood cells, red and white. White blood cells are probably the most important part of your whole immune system 

There are many different kinds of white blood cells in your body. They all work together to fight diseases