PHGY 210 Chapter Notes - Chapter 12.10-12.12: Extracellular Fluid, Starling Equation, Capillary Pressure
18 Mar 2017
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Velocity of capillary blood flow: branching of tubular structure influence velocity. If go from one large tube to smaller ones, total cross-sectional area small tubes greater but flow slower --maximizes time for exchange in capillaries. Diffusion across capillary wall: substances move between interstitial fluid and plasma through diffusion / vesicle transport / bulk flow, mediated transport also sometimes, like in brain. [c] > capillary plasma: local metabolic rate ultimately establishes transcapillary diffusion gradients. If tissue increases metabolic rate, need more nutrients and eliminate more wastes. [c] of plasma solutes except protein virtually same in filtered fluid and plasma. If total/final value is positive, favors filtration --if negative, favors absorption: pc and if directed outward, pif and c inward. If net outward pressure > inward pressure --> bulk filtration occurs, net filtration. If increase diameter of arterioles (i. e. exercise, skeletal muscle dilate), then outflow > inflow until new balance reached: arterioles are major resistance site of circulation --determine total peripheral.
