17 Cv Capillary Exchange

17 Cv Capillary Exchange - CAPILLARY EXCHANGE page 1...

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CAPILLARY EXCHANGE AC Brown page 1 A7b INTRODUCTION A. Functional Anatomy B. Functional Histology 1. Single layer of endothelial cells 2. Dimensions diameter: 5-10 uM length: 0.5-1 mm (blood cell velocity approximately 0.3-1.0 mm/sec) 3. Junctions between capillary cells normally "tight", but a. liver & bone marrow: large clefts between cells b. central nervous system: very tight ("blood-brain barrier") C. Properties 1. Short distance between each capillary and the cells it serves 2. Continual renewal of capillary blood by the circulation MOVEMENT ACROSS CAPILLARIES A. Mode: Simple diffusion, due to concentration difference between capillary blood plasma ("C c ") and tissue ("C t ") Note: The electrical force on charged particles is not important because there is only a small electrical potential difference across the capillary. Active transport generally does not occur, and when it does, it is too slow to be of major importance.
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CAPILLARY EXCHANGE AC Brown page 2 A7b MOVEMENT ACROSS CAPILLARIES (continued) B. Capillary Permeability 1. Selectivity: based only on size of the particle. All particles smaller than plasma proteins readily pass through capillary walls 2. Exceptions: In very tight capillaries, even small ions pass only slowly through the capillary wall. In open capillaries, even plasma proteins and cells can pass through the capillary wall C. Composition of Interstitial Fluid Because only large particles are filtered out by the capillary
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This note was uploaded on 01/03/2012 for the course BIO 308 taught by Professor Acbrown during the Spring '10 term at Portland.

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17 Cv Capillary Exchange - CAPILLARY EXCHANGE page 1...

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