Hydrostatic pressure forces water out of capillary beds while osmotic pressure pulls water in (due to the colloidal osmotic pressure of the blood). At the arterial end, the hydrostatic pressure is greater than the osmotic pressure and water moves out. The elastic deformation of arteries stores potential energy to supply continuous pressure.At the venous end, water moves in. But because more fluid moves out at the arterial end than returns at the venous end, the lymphatic system is required to return the fluid to blood vessels.

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