The lymphatic system does several jobs in the body. It
- Drains fluid back into the bloodstream from the tissues
- Filters lymph
- Filters the blood
- Fights infections
As the blood circulates, fluid leaks out from the blood vessels into the body tissues. This fluid is important because it carries food to the cells and waste products back to the bloodstream. The leaked fluid drains into the lymph vessels. It is carried through the lymph vessels to the base of the neck where it is emptied back into the bloodstream. This circulation of fluid through the body goes on all the time.
The lymph nodes filter the lymph fluid as it passes through. White blood cells attack any bacteria or viruses they find in the lymph as it flows through the lymph nodes. If cancer cells break away from a tumour, they often become stuck in the nearest lymph nodes. This is why doctors check the lymph nodes first when they are working out how far a cancer has grown or spread.
This is the job of the spleen. It filters the blood to take out all the old worn out red blood cells and then destroys them. They are replaced by new red blood cells that are made in the bone marrow. The spleen also filters out bacteria, viruses and other foreign particles found in the blood. White blood cells in the spleen attack bacteria and viruses as they pass through.
When people say "I'm not well, my glands are up" they are really saying they have swollen lymph nodes because they have an infection. The lymphatic system helps fight infection in many ways such as
- Helping to make special white blood cells (lymphocytes) that produce antibodies
- Having other blood cells called macrophages inside the lymph nodes which swallow up and kill any foreign particles, for example germs
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