1. Blood is under high pressure as it flows through the capillary network, forcing fluid out into the tissue and becoming tissue fluid. This fluid contains useful substances like oxygen and nutrients essential for the cells. Blood cells and large proteins remain in the capillary.
2. As the blood becomes deoxygenated, pressure is reversed and some of the fluid contain waste products will re-enter the capillaries and be carried away.
3. Excess fluids, waste products and large molecule – like proteins that were unable to re-enter the blood are taken up by lymph capillaries and carried to lymph nodes where the fluid is processed and enters back into the blood nearer the heart.