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The lymphatic system plays an important part in human biology. It:

The lymphatic system works closely with the circulatory system.

As you can see in the video to the left, fluid leaves the circulatory system (red) via the capillaries and becomes interstitial Fluid. 90% of the fluid re-enters the circulatory system due to the differences in concentration, but 10% enters open ended lymphatic Vessels (purple).

This is why we call the lymphatic system an open system.

Click here for an image

Once in the lymphatic vessels, the interstitial Fluid is called ‘lymph’.

The smaller open ended vessels eventually join up, creating larger vessels. They carrier the lymph to Lymph nodes.

Through out the lymphatic system are many lymph nodes.

A few of the common places Lymph Nodes are found are:  

The lymph nodes are the sight for the detection of pathogens and cancer cells. They are packed with B and T cells, Macrophages and other immune cells.

This is why your doctor may feel under your jaw or armpit when you are sick. These lymph nodes swell up.

In the circulatory system we have a heart to pump around the blood, but we don’t have one in the lymphatic system. So how dose the lymph travel?

Through out the lymph vessels are valves, which prevent back flow. Around these vessels are smooth muscles which contract and push the lymph through.
Skeletal muscles (voluntary movement) also cause lymph to flow.

This is why when you don’t move for a long time, (on a very long flight) your feet swell  

Over 2 litres of fluid passes through the lymphatic system everyday. That’s impressive considering our total blood volume is 5 litres.

Once the lymph is filtered and scanned for pathogens it is pumped back into the large veins near the heart.

Within the mammalian immune system there are primary lymphoid organs (bone marrow and thymus) which produce new lymphocytes. Secondary lymphoid organs (node, spleen , tonsils and adenoids) are where the immune response occurs.

Click here to learn more about the immune system

Click here for questions on the lymphatic system

Possible one of the most well known examples of a damaged lymphatic system is Elephantiasis.

It is caused by 3 types of specific ring worms which affect the lymphatic system. The long threadlike worms block the body’s lymphatic system.

The blocking causes the fluid to collect in the tissue, which makes the arm, leg or genitalia swell.

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