PHGY 214 Lecture Notes - Lecture 1: Extracellular Fluid, Oncotic Pressure, Body Water
12 May 2016
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Movement of water across a semi-permeable membrane down its own concentration gradient toward the area of higher solute concentration. Identify the major osmoles in the body and where each is found. Osmotic pressure is a measure of the tendency for water to move into a solution because of its relative concentration of nonpenetrating solutes and water. Net movement of water continues until the opposing hydrostatic pressure exactly counterbalances the osmotic pressure. Each mmole creates an osmotic force of 1mosmol. Osmolarity mosmol/l thus depends on number not size (volume) Osmolality mosm/kg h2o dependent on mass. * the two are used interchangeably except temperature changes osmolarity (heat causes expansion) *** ecf osmolarity = 300 mosmol/l: compare the effects of penetrating and non-penetrating solutes on the osmotic pressure exerted by each of these with respect to cells. Penetrating solutes are not effect osmoles and do not contribute to osmotic pressure.
