Edema
The filtration pressure is usually larger than the opposing forces, so a larger volume of fluid enters the tissues than is removed from them. The lymph vessels remove this excess fluid.
Fluid diffuses into the lymph vessels, and then when the tissue moves the fluid is squeezed past valves, which will not allow it to return to the tissues. The lymphatic fluid flows up to the lymph nodes, where white blood cells remove pathogens from it, and then is emptied back into the venous blood returning to the heart.
A constant flow of fresh fluid passes over the tissues - from the capillaries, over the cells, and to the lymph vessels.
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