PHSI2005 Final: microcirculation
15 Jan 2019
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Document Summary
30-500 um, resistance vessels, innervated by sympathetic nerves (cid:198) vasoconstriction by 1 (cid:120) capillaries consist of a single layer of endothelial cells, i. d. 8 um, exchange vessels (cid:120) pre-capillary sphincters (bands of smooth muscle) open in response to increase in metabolite concentrations (cid:120) e. g. Important avenue for blood to flow when capillary bed is closed off: substances can still diffuse to cells, but the distance of diffusion is larger and less efficient. Note: lactate, k+ and adenosine are metabolites in working muscle. Note: while vasoactive metabolites cause vasodilation in every other tissue, lungs act in the opposite way (cid:198) results in vasoconstriction. Phsi2005/2905 notes: explain how in a given region the total capillary flow, and the total surface area available for exchange, can be independently controlled. Interstitial fluid = 75% of extracellular fluid (cid:120) (cid:120) Co2) direct diffusion through membrane of endothelial cells.
