HHP 3500 Lecture Notes - Lecture 27: Extracellular Fluid, Endothelium, Flow Velocity

• School: University of Iowa
• Department: Health and Human Physiology
• Course: HHP 3500
• Professor: Peterson Clayton

Document Summary

Single layer of endothelial cells with thin basement membrane. Arterioles metarterioles precapillary sphincters (hook that connects arterioles to capillaries) capillary. 5% of blood in capillaries at any given time. Pressure decreases as we go into capillaries, about 25 mmhg: function- Lipid soluble substances (o2 and co2, and fatty acids, steroid hormones) diffuse through the endothelial cells. Ionic/polar (glucose, sodium, potassium) substances use gaps/channels/intracellular clefts to get between endothelial cells. Exception: large plasma proteins (globulins), too large to move across capillary wall, cannot fit through cleft: therefore these remain in vasculature, do not go out to cells. Concentrations within blood are stable, but concentrations in tissue change, which changes the rate of diffusion. As tissues use more o2, their concentrations go down, so diffusion into tissue increase. Bulk flow of protein free-fluid (because proteins are too big to move) from plasma to interstitial fluid or vice versa, changes the distribution of ecf.