38 Gas Exchange & Transport

38 Gas Exchange & Transport - Gas Exchange & Gas...

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Unformatted text preview: Gas Exchange & Gas Transport Outline- How much O 2 & CO 2 is in air & alveoli?- What determines how much gas dissolves into sol’n?- How much O 2 and CO 2 is in the blood?- How is O 2 transported in the blood?- How is CO 2 transported in the blood? Textbook reading: 598-611 Overview of Gas Exchange Last class: passage of air thru airways 1) Gas exchange in the lungs at alveoli: diffuse into bloodstream → circulate thru blood 2) Gas exchange at tissues of body: O 2 diffuses in & CO 2 (pdct of cellular metabolism) out 3) Gas transport in respiratory system thru blood 1. a) How much O 2 & CO 2 is in air?- Dalton’s law of partial pressures: Total atmospheric pressure = the PB = PO 2 Partial Pressure = Fractional Conc e.g . PO 2 = FO 2 X PB 2 2 PB is normall FO 2 = 21% PO 2 = 159.6 mmHg sum of the partial pressures 2 + PCO 2 + PN 2 centration X Total Pressure PCO 2 = FCO 2 X PB 2 2 y 760 mmHg FCO 2 = 0.04% PCO 2 = 0.3 mmHg “PB”: atmospheric or barometric pressure I.e. at sea lvl: PB = 760 mmHg- Total pressure = sum of individual pressures of gases composing atmosphere- Note: Fractional conc° applies to gases only; conc° applies to gases in liquids like blood- PO 2 = ~160mmHg for dry air, PCO 2 = 0.3mmHg But air is rapidly humidiFed in respiratory tract- Water vapour pressure (PH 2 O = 47mmHg always) contributes to overall pressure- So to determine 100% humidiFed air pressure = PB - PH 2 O PB = PO 2 + PCO 2 + PN 2 + PH 2 0 ( 2 2 2 2 760 mmHg – 47 mmHg = 713 mm 47 mmHg) Hg- Partial pressure = (fractional concentration) x (total pressure)- PO 2 differs for 100% humidiFed air = 150mmHg, PCO 2 = 0.29 mmHg e.g . PO 2 = FO 2 X PB Pressure is 7 Pressure is 7 FO 2 = 21% PO 2 = 150 mmHg PCO 2 = FCO 2 X PB 13 mmHg 13 mmHg FCO 2 = 0.04% PCO 2 = 0.29 mmHg Lectu Respirato s Airways and lungs alveoli Mus pleura Respirato fun Pulmonary ventilation Gas excha Gas excha alveoli/blo blood/tiss ¡ pressures lung how much? properties Respiratory contr Exercise an ure 3 ory system structures scles Pulmonary circulation ory system nctions ange Gas Defense Vocalization ange ood ues Gas transport Acid/base balance O 2 CO 2 + H 2 H + + HCO3 ¡ ol nd High Altitude PSL302: Lecture 38, by ¡rench ¡riday, Jan. 14, 2010 1 of 8 1. b) How much oxygen & carbon dioxide is in alveoli?- This is what you’d breathe in as fresh air, but you’re not exchanging entire V lung as you breathe- Tidal volume = 500mL of fresh air, + dead air- By the time the air gets to alveoli, partial pressures are:- PO 2 = 100 mmHg- PCO 2 = 40 mmHg (much higher: CO 2 from body builds up in alveoli)- Now : how does gas dissolve into the blood for gas exchange? 2. What determines how much gas dissolves into sol’n?...
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This note was uploaded on 03/27/2012 for the course PSL 301 taught by Professor Mackayfrench during the Winter '12 term at University of Toronto.

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38 Gas Exchange & Transport - Gas Exchange & Gas...

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