Concentrations of plasma proteins and salt found in capillaries create osmotic pressure, which is necessary for fluids to transfer from the capillary to bodily tissues. This fluid transfer is performed through a process known as diffusion.
Capillaries are small blood vessels that allow fluids, gases and other nutrients to be transferred from the bloodstream into tissues and organs throughout the body. Pores found along the capillary wall allow substances to enter or exit the bloodstream while maintaining the osmotic and blood pressure by preventing the release of the plasma proteins and salt from the capillary.
Diffusion is a process in which concentrated molecules separated from an area with less concentrated molecules are allowed to enter that area by utilizing the internal energy of the molecules. Osmosis is a type of diffusion caused by osmotic pressure, in which a solution and a solvent are separated by a membrane that can allow molecules to pass through under the right conditions. Capillary beds have an arteriole end in which the blood pressure is greater than the osmotic pressure, causing molecules to pass through the end into the desired area, while the osmotic and blood pressures in the center of the capillary bed are equally balanced, which allows substances to freely enter or exit through the capillary wall.