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Fluid Movement - Physiology (view source)
Revision as of 13:59, 12 August 2008
, 13:59, 12 August 2008no edit summary
The osmolarity of a solution is inversely proportional to the water concentration. Water tends to flow from an area of lower osmolarity to an area of higher osmolarity. Until the osmolarity of both is equal. If the osmolarity of the ECF is changed say after a meal high in salt then because the ECF now has a higher osmolarity than the interstitial fluid water moves from the interstitium into the ECF until a neq equilibrium is reached. Water in turn flows out of the intracellular fluid into the interstitium as this now has a higher osmolarity. Thus cell volume changes.
The osmolarity of a solution is inversely proportional to the water concentration. Water tends to flow from an area of lower osmolarity to an area of higher osmolarity. Until the osmolarity of both is equal. If the osmolarity of the ECF is changed say after a meal high in salt then because the ECF now has a higher osmolarity than the interstitial fluid water moves from the interstitium into the ECF until a neq equilibrium is reached. Water in turn flows out of the intracellular fluid into the interstitium as this now has a higher osmolarity. Thus cell volume changes.
The changes in cell size are quickly corrected by transport processes. If osmolarity is constant then the volume of each compartment of the body is determined by how many particles of solute are dissolved there. The relationship is expressed by the following formula:
Concentration = Number of dissolved particles ÷ volume
==Water Replacement==
When water is ingested it actually takes a rather long time (30-60mins) before the equilibrium is reset between the ECF and ICF. This is mainly because it takes time to distribute the water between the organs of the body after it is absorbed.