What drives fluid movement into the arterial end of a capillary?

Hydrostatic pressure is the primary force driving fluid movement into the arterial end of a capillary. This pressure is generated by the pumping action of the heart, which pushes blood into the capillaries, causing blood to exert a force against the capillary walls. As a result, this pressure encourages the movement of fluid (including water and nutrients) out of the capillaries and into the surrounding tissue.

At the arterial end of the capillary, the hydrostatic pressure is typically higher than the osmotic pressure, promoting the filtration process where fluid leaves the capillary. This process is vital for nutrient delivery to tissues and for maintaining fluid balance within the body.

Other pressures, such as oncotic pressure, which is related to the presence of proteins in the plasma, play a role in pulling fluid back into the capillary at the venous end. However, it is the hydrostatic pressure at the arterial end that is the main driving force for fluid movement out of the capillaries. Blood viscosity does not directly influence fluid movement in this context.