How does the lymphatic system work?

Large amounts of plasma, the liquid component of the blood, seep out through the thin walls of the capillaries regularly. This fluid carries oxygen, nutrients, and cellular waste. The surrounding tissues absorb the oxygen and nutrients while leaving behind the unwanted waste. 

In a cleanup attempt, the plasma collects the waste and returns it to the bloodstream through the same pores in the capillary walls. Most of the plasma re-enters the bloodstream in this manner. The remaining plasma, which does not re-enter the bloodstream and is still in the tissues, is collected by tiny lymphatic capillaries. During its journey, this fluid changes its name from plasma to lymph. 

The lymphatic capillaries then transfer the lymph into larger vessels known as lymphatic vessels, which move the lymph along until it reaches one of two main ducts in the upper chest: the right lymphatic duct and the thoracic duct. These ducts merge into large veins called the subclavian veins, where the lymph is emptied. The lymph reenters the bloodstream from here and is ready to circulate through the body again.