Final answer:
The forces that tend to move fluid out of the blood vessel are blood hydrostatic pressure and interstitial fluid hydrostatic pressure. Blood hydrostatic pressure pushes fluids out of capillaries, and interstitial fluid hydrostatic pressure opposes this movement but is typically lower, allowing for filtration.
Step-by-step explanation:
The two forces that tend to move fluid out of the blood vessel are blood hydrostatic pressure and interstitial fluid hydrostatic pressure. The blood hydrostatic pressure is the pressure exerted by the blood on the walls of the blood vessels, which is caused by the pumping action of the heart. This pressure is higher at the arteriolar end of the capillary, forcing plasma and nutrients out of the capillaries into the surrounding tissues.
On the other hand, the interstitial fluid hydrostatic pressure (IFHP), although generally lower, opposes the blood hydrostatic pressure and rises as fluid exits a capillary. The movement of fluid out of the capillary and into the interstitial space, largely influenced by these pressures, is called filtration.