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The Microcirculation & Lymphatic System. Structure of the Microcirculation. Capillary System Metarterioles Precapillary sphincter Large “preferential channels” Small “true capillaries”. Structure of the Microcirculation. Metarteriole. Preferential Channel. Arteriole.
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Structure of the Microcirculation • Capillary System • Metarterioles • Precapillary sphincter • Large “preferential channels” • Small “true capillaries”
Structure of the Microcirculation Metarteriole Preferential Channel Arteriole Precapillary Sphincter True Arterioles Venule
Structure of the Microcirculation (1 Endothelial Cell Thick) Plasmalemmal Vesicles Endothelial Cell Vesicular Channel? Basement Membrane (Collagen Type I) Intercellular Cleft
Transport Mechanisms • Diffusion • Intercellular Clefts • Plasmalemmal Vesicles • “Tight Junctions” (brain) • Open Junctions (liver) • Fenestra (kidney)
Capillary Vasomotion • Intermittent flow regulated by precapillary sphincters. • Controlled by O2 concentration.
Diffusion through Capillary Membrane • Lipid soluable – through endothelial cell membrane. • Water soluable – through intercellular pores • Size Dependent
Diffusion through Capillary Membrane This figure illustrates that the permeability of substances through capillary membrane decreases roughly with the logarithm of size.