Lymph is a clear fluid that travels through your body's arteries, circulates through your tissues to cleanse them and keep them firm, and then drains away through the lymphatic system.
Lymph nodes are the filters along the lymphatic system. Their job is to filter out and trap bacteria, viruses, cancer cells, and other unwanted substances, and to make sure they are safely eliminated from the body.
Also traveling through the arteries is fresh blood, which brings oxygen and other nutrients to all parts of the body—including your breasts. Used blood leaves the breasts through the veins and is pumped back to the heart and lungs to be refreshed. Lymph must also be refreshed and recycled. Lymph drains away from your breasts through the lymphatic system, which is made up of lymphatic channels and lymph nodes.
"The arteries are like a two-lane highway bringing nutrients, oxygen and fluid to the breast. The vein is a one-lane highway taking away the used blood, and the lymphatic channels are the other one-lane highway draining away the lymph fluid. Two lanes in together, but two separate lanes out."-- Marisa Weiss, M.D., chief medical officer, Breastcancer.org