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Fluid Movement - Physiology (view source)
Revision as of 17:12, 20 August 2008
, 17:12, 20 August 2008→The Effects of [[Useful definitions - Renal Anatomy & Physiology| Osmolarity]]
These forces play differant roles depending on the structure being crossed. Both influence passage across capillary walls however only osmotic pressure influences that movement across cell membranes. The reason hydrostatic pressure has little influence over the transport across cell membranes is that the hydrostatic pressure of the intracellular and interstitial fluid is relatively constant.
These forces play differant roles depending on the structure being crossed. Both influence passage across capillary walls however only osmotic pressure influences that movement across cell membranes. The reason hydrostatic pressure has little influence over the transport across cell membranes is that the hydrostatic pressure of the intracellular and interstitial fluid is relatively constant.
==The Effects of [[Useful definitions - Renal Anatomy & Physiology| Osmolarity]]==
==[[Useful definitions - Renal Anatomy & Physiology| Osmolarity]]==
===What is Osmolarity===
It is a term which is commonly used to represent the osmotic properties of a solution. It is the total number of osmotically active molecules of solute per litre of solvent and its unit is osmol/l. For example a solution with 1 milliosmol of glucose has an osmolarity of 1 milliosmol/l because glucose is an osmotically active molecule. However a solution with 1 milliosmol of NaCl has an osmolarity of 2milliosmol/l because in solution NaCl dissociates and each ion is osmotically active.
===The Effects of Osmolarity===
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.