PHYL2001 Lecture Notes - Lecture 7: Extracellular Fluid, Microcirculation, Endothelium
Document Summary
The microcirculation consists of: arterioles, venules, metarterioles, capillaries, arteriovenous shunts. Transport can be: between cells or transcellular, active or passive, bulk flow or diffusion lipid soluble substances pass across the cell. Small-medium sized water soluble substances substances e. g. oxygen, carbon dioxide, anaesthetics, ethanol diffuse between endothelial cells. e. g water, sodium ions, chloride ions, calcium ions, urea, glucose, lactate, adh (vasopressin), insulin. Large substances can be moved by pinocytosis e. g. lipoproteins cross the capillary wall. Small water-soluble substances pass through the pores. Exchangeable proteins are moved across by vesicular transport. Interstitial fluid can flow into and out of capillaries. Fluid (hydrostatic) pressure inside the capillary pushes plasma out. Plasma proteins stay in capillary so total soluble concentration is higher in plasma than in interstitial fluid. Colloidal osmotic pressure pulls interstitial fluid in. Gas exchange is by diffusion thought cells, other substance exchange by diffusing between cells or by pinocytosis. Total osmotic pressure of blood includes all solutes including salts: 6000 mmhg.
