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27 Gas exchange - Biology141(Physiology 1:15 AM...

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4/6/08 1:15 AM Biology141 (Physiology) Page 1 of 4 https://courses.bio.psu.edu/spring2008/biol141/Lecture%2027(2008).htm Biology141 (Physiology) Lecture 27 M. Whim RESPIRATORY SYSTEM - GAS EXCHANGE [1]. BACKGROUND. the amount of a gas in the air or blood is measured by its partial pressure ( P ). atmospheric pressure = 760 mm Hg. O 2 comprises ~ 21% of the atmosphere. Thus what is the PO 2 of atmospheric air? (a). How much O 2 and CO 2 is in the blood? PO 2 in alveolar air = 105 mm Hg. PO 2 of blood arriving at the lungs = 40 mm Hg. PO 2 of blood leaving the lungs = 100 mm Hg (i.e. close to equilibrium & hemoglobin is almost completely loaded with O 2 ). what are the corresponding values for CO 2 ? (b). The movement of gases between the blood and the atmosphere. in the lungs gases diffuse down their concentration gradient until the partial pressure of the gas in the alveoli is the same as the partial pressure in blood. since PO 2 of alveolar air > PO 2 of blood, the blood picks up ( loads ) O 2 in the lungs.
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