Located at: en./wiki/File:Extracellular_Matrix.png. License: CC BY-SA: Attribution-ShareAlike Located at: License: CC BY-SA: Attribution-ShareAlike Located at: en./wiki/Intracellular_fluid%23Properties_and_composition. Located at: en./wiki/Interstitial_fluid%23Composition. Located at: en./wiki/File:Biological_cell.svg. License: Public Domain: No Known Copyright Located at: en./wiki/File:Ex.lar_Matrix.png. Located at: en./wiki/Intracellular_fluid. Located at: en./wiki/Extracellular_fluid. Located at: en./wiki/intracellular%20fluid. Located at: en./wiki/extracellular%20fluid. Located at: en./wiki/bioelec.nce%20analysis. Located at: en./wiki/Bioelectrical_Impedance_Analysis. License: CC BY-SA: Attribution-ShareAlikeĬC LICENSED CONTENT, SPECIFIC ATTRIBUTION The Starling Equation is mathematically described as Flux=Kf. Note how the concentration of interstitial solutes increases proportionally to the distance from the arteriole.Īccording to Starling’s equation, the movement of fluid depends on six variables: This equation has a number of important physiologic implications, especially when disease processes grossly alter one or more of the variables.Ĭapillary dynamics: Oncotic pressure exerted by the proteins in blood plasma tends to pull water into the circulatory system. If negative, fluid will tend to enter the capillary (absorption). If positive, fluid will tend to leave the capillary (filtration). The solution to the equation is known as the net filtration or net fluid movement. The Starling equation defines the forces across a semipermeable membrane to calculate the net flux. The Starling model: Note the concentration of interstitial solutes (orange) increases proportionally to the distance from the arteriole.Ĭapillary permeability can be increased by the release of certain cytokines, anaphylatoxins, or other mediators (such as leukotrienes, prostaglandins, histamine, bradykinin, etc.) that are released by cells during inflammation. This difference is created by the direction of the flow of blood and the imbalance in solutes created by the net movement of water that favors the tissue fluid. At the arterial end of a vessel, the hydrostatic pressure is greater than the osmotic pressure, so the net movement favors water and other solutes being passed into the tissue fluid.Īt the venous end, the osmotic pressure is greater, so the net movement favors substances being passed back into the capillary. The balance between the two forces differs at different points on the capillaries. Because the blood in the capillaries is constantly flowing, equilibrium is never reached. The osmotic pressure drives water back into the vessels. The water passes from a high concentration (of water) outside of the vessels to a low concentration inside of the vessels, in an attempt to reach an equilibrium. The water potential is created due to the ability of the small solutes to pass through the walls of capillaries. It pushes water out of the small tight junctions in the capillaries. Hydrostatic pressure is generated by the contractions of the heart during systole. How fluid moves through compartments depends on several variables described by Starling’s equation.
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