The Lymphatic System is a secondary path for fluid to return back to the heart. It runs parallel to the veinous system, picking up molecules within the cells that cannot diffuse back into the circulatory system. It is the lymphatic system that cleans the interstitial space of wastes, water, fat, bacteria, viruses and any other foreign particle.

The lymphatic system is also part of the immune system. It is through the lymph nodes of the lymphatic system that lymph is filtered, removing the foreign particles and viruses allowing the white blood cells to destroy the unwanted body.