There are four primary means that water and other small molecules cross into or out of cells. They are reviewed here since they play such an important role in body fluids and many other physiological functions. Diffusion Powered by random movement of molecules in a solution Net movement is from regions of high concentration to low.
Diffusion can occur through tight junctions or within bulk solutions.
Diffusion of water down its concentration gradient is called osmosis. You're missing a great java demo of diffusion Anions and cations shown moving at random, as via diffusion in a solution. Put the cursor over the box above to start the simulation. Click within the box to reset all the particles to a single point. For a more extensive review of Diffusion, Osmosis, and Nernst Potentials, see my separate chapter on that subject.