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Movement Across a

Semi-permeable Membrane

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Osmosis

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Osmotic Pressure depends on

Concentration of Particles

= cRT

Jacobus Henricus Vant Hoff1852-1911

= icRT

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Effective Osmotic Pressure depends on

Concentration of ImpermeantSolutes

= icRT

= icRT

= Reflection coefficient( 0 - 1 )

permeable - impermeable

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Reflection Coefficient (

)Permeability of a membrane to a particularsolute, compared to water

= 1-P solute

P water

Effective Osmotic Pressure = Tonicity

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HydrostaticPressure

Water Movement

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Osmotic Pressure

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Osmoles = # of Active Particles

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Osmotic Composition of Body Fluids

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Osmotic Pressure

mmHg = osmolarity x 19.3

= cRT

300 mOsm/Lx 19.35790 mmHg =

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Volume of a Compartment is

determined by the # of Osmoles

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What Drives Fluid Movement?Intracellular Extracellular

Interstitial

Plasma

in Osmolarity

inPressures

CellMembrane

CapillaryWall

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Pressures Across Capillary

Jv = Kfx net filtration pressure

Jv = Kfx (HPc-HPi)-(c- i) Kf= S.A. x Lp

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