Editing Large intestine (section)

===Standing gradient osmosis===
Water absorption at the colon typically proceeds against a [[Route of administration#Application location|transmucosal]] [[osmotic pressure]] [[Osmosis#Osmotic gradient|gradient]]. The '''standing gradient osmosis''' is the reabsorption of water against the osmotic gradient in the intestines. Cells occupying the intestinal lining pump sodium ions into the intercellular space, raising the osmolarity of the intercellular fluid. This [[Tonicity|hypertonic]] fluid creates an osmotic pressure that drives water into the lateral intercellular spaces by osmosis via [[tight junction]]s and adjacent cells, which then in turn moves across the [[Basal lamina|basement membrane]] and into the [[Capillary|capillaries]], while more sodium ions are pumped again into the intercellular fluid.<ref>{{cite web | url=http://www.vivo.colostate.edu/hbooks/pathphys/digestion/smallgut/absorb_water.html | title=Absorption of Water and Electrolytes}}</ref> Although water travels down an osmotic gradient in each individual step, overall, water usually travels against the osmotic gradient due to the pumping of sodium ions into the intercellular fluid. This allows the large intestine to absorb water despite the blood in capillaries being [[Tonicity|hypotonic]] compared to the fluid within the intestinal lumen.