A new view of Starling's hypothesis at the microstructural level.
Item
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Title
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A new view of Starling's hypothesis at the microstructural level.
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Identifier
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AAI9959187
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identifier
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9959187
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Creator
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Hu, Xiaping.
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Contributor
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Mentors: Sheldon Weinbaum | Fitz-Roy Curry
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Date
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2000
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Language
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English
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Publisher
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City University of New York.
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Subject
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Engineering, Biomedical | Engineering, Mechanical
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Abstract
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Starling's hypothesis is the basic principle in physiology, which describes the fluid movement across microvessels. In contrast to the widely accepted view that the fluid is filtered out of the arterial side of the capillary and reabsorbed at the venous end leaving a small net filtration which is removed by the lymphatics, we have developed a new mathematical model at the cellular microstructural level which theoretically predicts that there is no sustained venous; absorption even at very low capillary pressures. We have also proposed that the forces for filtration and oncotic reabsorption across the capillary wall are determined by the local difference in the hydrostatic and colloid osmotic pressure across the endothelial surface glycocalyx, the primary molecular sieve for plasma proteins, rather than the global difference in hydrostatic and oncotic pressure across the entire vessel wall between the plasma and tissue, as has been universally assumed until now. This subtle, but important modification, leads to a major revision of the Starling equation. Here, new theoretical and experimental results on individually perfused microvessels are presented to demonstrate that the effective oncotic; pressure across the capillary endothelium is not the global difference in oncotic pressure between blood and tissue.;We also investigate the effect of a parallel non-convective transcellular pathway on the transcapillary fluid filtration due to vesicular transport. The model predicts that the local protein concentration behind the surface glycocalyx can differ greatly from the interstitial protein concentration, since the presence of the junction strand prevents back diffusion of the proteins into the shielded cleft region between the backside of the surface matrix and the lumen side of the junction strand. Even though the presence of a nonconvective pathway may greatly increase the interstitial protein concentration, there is only a modest effect on the local concentration at the backside of surface glycocalyx and, thus, only small changes in the fluid filtration across the capillary. The net result is that the filtration in the capillaries is far less than, heretofore, realized and there may be no need for venous reabsorption.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
