This drawing indicates normal lines of lymphatic drainage.  

Stimulation of normal lines of drainage can increase lymphatic function to help reduce swelling and oedema.

The body is divided into sections, each section is called a ‘lymphotome’

There are four main lymphotomes in the trunk of the body, you can see them in the drawing divided by the blue lines.

The blue lines indicate areas called ‘watersheds’. The arrows show  the direction and to which drain point lymphatic fluids (lymph) in the tissues are removed in a  normally functioning body.

Lymph derived from the interstitial tissues in each lymphotome drains to either points A or B and is transported via the lymphatic system to return back into the the blood circulation for processing in kidneys and liver.  Fluid does not naturally cross the watersheds between the  lymphotomes or across the centerline, you can however make it do this with massage.

When a lymphotome’s drainage point becomes blocked due to impediment, as in most secondary lymphoedemas, then oedema  occurs. This oedema if long term develops into lymphoedema and may eventually cause sufficient swelling for the skin to rupture and release fluid causing an open fistulae.

In the case of primary  lymphoedema the  lymphatics may not work well enough to prevent oedema formation without additional assistance and dietary changes.