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The Blood & Circulation The Lymphatic System The Immune System
What is the lymphatic system?
The lymphatic system is a system of thin tubes that runs throughout the body. These tubes are called 'lymph vessels'. You may also hear them called 'lymphatic vessels'.
The lymphatic system is like the blood circulation - the tubes branch through all parts of the body like the arteries and veins that carry blood. Except that the lymphatic system carries a colourless liquid called 'lymph'.
Lymph is a clear fluid that circulates around the body tissues. It contains a high number of lymphocytes (white blood cells). Plasma leaks out of the capillaries to surround and bathe the body tissues. This then drains into the lymph vessels.
The fluid, now called lymph, then flows through the lymphatic system to the
biggest lymph vessel - the thoracic duct. The thoracic duct then empties
back into the blood circulation.
Lymph glandsAlong the lymph vessels are small bean-shaped lymph glands or 'nodes'. You can probably feel some of your lymph nodes.
There are lymph nodes 
Under your arms, in your armpits In each groin (at the top of your legs) In your neck There are also lymph nodes that you cannot feel in
Your abdomen Your pelvis Other organs that are part of the lymphatic systemThe lymphatic system includes other body organs. These are the
Spleen Thymus Tonsils Adenoids 
The spleen is under your ribs on the left side of your body. The spleen works as a filter of lymph fluid.
The thymus is a small gland under your breast bone. The thymus helps to produce white blood cells. It is usually most active in teenagers and shrinks in adulthood.
The tonsils are two glands in the back of your throat. The tonsils and adenoids (also called the 'nasopharyngeal' tonsils) help to protect the entrance to the digestive system and the lungs from bacteria
and viruses.
The adenoids are at the back of your nose, where it meets the back of your throat.
What does the lymphatic system do? The lymphatic system does three main jobs in the body. It:
Drains fluid back into the bloodstream from the tissues Draining fluid into the bloodstream
As the blood circulates, fluid leaks out 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 is going on all the time.
Filtering lymphThis is the job of the spleen. It filters the lymph to take out all the old worn out red blood cells. These are destroyed and replaced by new red blood cells that have been made in the bone marrow.
Fighting infectionWhen 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
This function of the lymphatic system is really part of the immune system.