Intra Vascular and Extra Cellular Spaces

The cell membrane dictates what can go in and out. The interstitial space is just all the flor around the e alth, all the space between the cells and around the cells. But then there's also the volume of fluid in your vascula. So even though it sub categorize the extra cellular space as sub sub categorie - most of the stuff in the plasma, all this fluid, this watery stuff, can just move in and out a tets.