How is tissue fluid and lymph formed?

At the arteriole end:The blood in the capillary has a high hydrostatic pressure due to the inherently high pressure in the blood vessels (due to ventricular contraction). Hydrostatic pressure would tend to push water out of the blood.At the same time the water potential of the blood is lower than the tissue fluid, so this would tend to push water in the opposite direction - out of the tissue fluid.However, the hydrostatic pressure is greater than the osmotic pressure so there is a net movement of fluid out of the blood into the tissue fluid. This movement occurs through gaps in the capillary wall. Cells in the blood and proteins are too big to fit through these gaps so must remain in the blood.At the venous end:The blood in the capillary has lost a lot of its hydrostatic pressure because of the loss of fluid at the arteriole end.The blood still has plasma proteins, but now the water potential is much lower than in the tissue fluid - this would tend to move fluid back into the blood. There is also some hydrostatic pressure exerted by the tissue fluid. This means that there is now a net movement of fluid back into the capillary. However, not all of the tissue fluid is returned to the capillary at the venous end. There must be a mechanism to drain the rest - this is the lymphatic system. The lymph fluid travels in ducts (e.g. thoracic duct) and is returned to the subclavian vein.