Answer the following question given this paragraph: 

Another mechanism besides diffusion to passively transport materials between compartments is filtration. Unlike diffusion of a substance from where it is more concentrated to less concentrated, filtration uses a hydrostatic pressure gradient that pushes the fluid—and the solutes within it—from a higher pressure area to a lower pressure area. Filtration is an extremely important process in the body. For example, the circulatory system uses filtration to move plasma and substances across the.


Q: What is used during filtration to push fluids and solutes, from higher pressure areas to lower pressure areas?


A:
hydrostatic pressure gradient