PHGY 209 Lecture Notes - Lecture 8: Starling Equation, Sodium Chloride
30 Oct 2016
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Determining the distribution of fluid between the plasma and the isf compartments by controlling trans capillary dynamics. Plasma and isf separated by capillary wall: freely permeable to h2o and ions. Isf and icf separated by cell membrane: impermeable to ions. Ecf is mostly na+ and cl: ecf may be approximated by 0. 9% solution of nacl, 300mosm, 6. 7 atmospheres, or 5100 mmhg, plasma has more protein than isf. For a net flow of water between compartments, there"s has to be a difference in osmotic pressure. Increasing nacl won"t make a difference in net flow of water. Only non-diffusible solutes contribute to the effective osmotic pressure of a solution: diffusible solutes do not since they become equally distributed on both sides of the membrane, plasma proteins are non-diffusible. Colloidal osmotic (oncotic) pressure (c. o. p) of plasma. Very small but only concentration that can give rise to an effective net movement. Increases: more water will flow into the plasma.
