at arteriole end of capillaries, the hydrostatic pressure is high ( due to contractions of left ventricle). Soluble plasma proteins in the blood reduce the water potential of the blood, creating a water potential gradient, which exerts a pulling force, opposing the loss of fluid from the capillary. However, the hydrostatic pressure is higher than the opposing water potential gradient. As a result, water and solutes are forced out of blood through the pores in capillary walls and this forms tissue fluid.