BIO 3302 Lecture Notes - Lecture 4: Tight Junction, Endothelium, Extracellular Fluid
16 Nov 2016
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Assu(cid:373)ptio(cid:374)s of poiseuille"s e(cid:395)uatio(cid:374): flow is laminar (i. e. layers of blood slide past each other smoothly) This applies reasonably well; most cells in circulatory system meet this requirement. We use turbulent flow to measure blood pressure. Comparing blood to water, plasma is more viscous than water, and blood is more viscous than plasma (3-4x viscosity of water) This can become a problem; when thinking about resistance, it is dependent on length, viscosity, and inversely proportionate to radius4; Increase in resistance results in increase in viscosity: a viscous fluid flowing through small diameter vessels results in high resistance, we would think that this would happen in the circulatory system, but this is not the case: Instead of going up, viscosity actually goes down when blood passes through small radius tubes; This lowers viscosity in small vessels, lowering resistance and work that the heart has to do to in pumping blood to the body through circulatory system.
