osmolarity and tonicity

• the cell will shrink when the solution is hyperosmotic.
• the cell will swell when the solution is hypo-osmotic
• In a hypertonic solution a RBC will crenate (shrink)
• In a hypotonic solution a RBC will hemolyze (swell)
• The normal range for osmolarity is 280-300 mOsm
• The total body water is 60% of the person's weight (in liters)
• The ICF is 2/3 of the TBW and the ECF is 1/3 of it
• The plasma volume is 1/4 of the ECF volume
• Evans blue can also be considered as the plasma
• Interstital fluid

  3/4 of the ECF and is the fluid between the plasma and the ICF
• Osmolarity is the molarity x dissociation factor
• The dissociation factor is 2 for NaCl and is 1 for complex molecles like urea and glucose
• The osmolarity of NS is 308 mOsm (type in the number)
• penetrating particles can diffuse in which they go from high to low
• non penetrating particles cant pass through the membrane so the water level has to change based on the concentration
• There is more water where the non penetrating particles are
• water goes from low solute to high solute
• there is no concentration gradient in the cell when water and cell concentration are equal
• osmotic pressure is pressure due to water movement
• NaCl is a functionally non penetrating solute and proteins are completely non penetrating
• urea and glucose are penetrating particles but glucose is slowly penetrating
• concentration= solute / volume
• normal saline is iso tonic and iso osmotic
• D5W is iso osmotic and hypo tonic
• 1/2 NS is hypo tonic and hypo osmotic
• D5 1/2 NS is hyper osmotic and hypo tonic (this is due to the 1/2 NS being non penetrating)
• D5NS is hyper osmotic and iso tonic
• if the tonicity is 0 then the solution will be hypotonic
• tonicity only comes from non penetrating particles like NaCl