The lymphatic system plays an important part in human biology. It:
Controls fluid balance by draining and cleaning the fluid from the circulatory system.
Delivers fats to the circulation system
Plays a key role in the immune system.
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:
Groin
Armpit
Under the jaw and chin
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.
