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Unformatted text preview: Lecture 8: Exchange and Transport of Respiratory Gases General : o Exchange : movement of gases across barriers o Transport : carriage of gases in the blood Diffusion (exchange) of Gas Across a Barrier o there are barriers to diffusion o what influence the rate of movement in both directions Surface Area Thickness o A) Homogeneous Barrier Determines flow in both direction : SA of membrane concentration of partial pressure differences of gasses thickness/width of membrane Net flow : occurs when flow in one direction exceeds flow in other o B) Alveolar Wall Must consider moisture lines alveoli: includes necessity that gas is soluble in that liquid we have to know solubility constant of gas Henrys Law according to Henrys Law, amt of oxygen dissolved in liquid layer = [solubility Oxygen X its partial pressure Oxygen ] Thickness of Diffusion of Gas o Thicker barrier = slower diffusion of gas o Top vs Bottom picture: bottom thinner barrier steeper slope faster diffusion Top: thicker barrier longer slope slower diffusion produces low flow Multiple Diffusion Barriers for Alveolar Oxygen to Pass o shows multiple layers between alveolar layer and pulmonary capillary blood 3 important layers: type 1 alveolar cells interstitial space o separates alveolar epithelium from endothelium capillary endothelium these layers make up barrier to diffusion each segment has its own diffusion properties D1-D12: suggest each layer has different diffusion properties o D M : all of them summed is the diffusion property of membrane Slide 1 Slide 2 Slide 3 Slide 4 o : oxygen binding to Hb from OxyHb o D L : total diffusion capacity of the lung o Vc = volume of blood in pulmonary capillaries o theta: rate of uptake by Hb described by: volume, concentration, partial pressure Limitation of Diffusion and Perfusion: o there are limitation o perfusion : rate of blood flow o A) diffusion limited exchange of gas (left) uses low concentration of carbon monoxide binds to Hb o A) perfusion limited exchange of gas (right) uses nitrous oxide doesnt bind to Hb o B) Partial Pressure of Carbon Monoxide in Alveolar Air [Limitation] slope of both curves: Carbon M in blood never reaches equlibrium with Carbon M in alveolar air rate of diffusion across barrier is so slow and bound by Hb that the free CO in solution could never reach the alveolar concentration CO doesnt reach equilibrium with air CO goes to capillary w/o reach equilibrium o B) Partial Pressure of Nitrous Oxide in Alveolar Air [Limitation] represent nitrous oxide in alveolar air Hb doesnt bind so it stays in the solution amount of nitrous oxide quickly equlibrates with N2O in...
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This note was uploaded on 03/07/2012 for the course 830 201 taught by Professor Leyton during the Fall '08 term at Rutgers.
- Fall '08