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Gas Exchange
From Ch. 42
08 April 2015 1Gas-Exchange.ppt
08 April 2015 Gas-Exchange.ppt 2
Animal Life
• Four critical processes• Obtain energy and material• Ingest, digest, absorb
• Obtain oxygen
• Dispose of nitrogenous waste• NH3, urea, uric acid
• Dispose of CO2
Animal Life
• Multicellular organisms• Internal circulation
• Coordination, information transfer
• Structural maintenance
• Movement
• Maintenance of homeostatic internal environment
08 April 2015 Gas-Exchange.ppt 3
08 April 2015 Gas-Exchange.ppt 4
Gas Exchange
• Exchange of O2 for CO2 occurs by diffusion
• Structure of gas exchange organs facilitates diffusion
08 April 2015 Gas-Exchange.ppt 5
Gas Exchange
• To, temperature
• S, solubility
• mol. wt., molecular weight of diffusing gas
• r, rate of diffusion
• P, difference in partial pressure (O2 or CO2)
• A, area of exchange membrane
• d, distance
Gas Exchange Systems• Gills in aquatic & marine animals
Large area Hemoglobin & other oxygen transporters pO2 variable in water
08 April 2015 Gas-Exchange.ppt 6
Gas Exchange Systems
08 April 2015 Gas-Exchange.ppt 7
• Fish gill• Filaments with large area
• Countercurrent flow maintains ΔP
Gas Exchange Systems
08 April 2015 Gas-Exchange.ppt 8
• Fish gillCountercurrent flow maintains ΔP
Gas Exchange Systems
08 April 2015 Gas-Exchange.ppt 9
• Tracheal systems of arthropods• large area
• Ventilation (?) to maintain ΔP
Gas Exchange Systems
08 April 2015 Gas-Exchange.ppt 10
• Lungs in mammals• Diaphragm & other muscles for ventilation
Gas Exchange Systems
08 April 2015 Gas-Exchange.ppt 11
• Lungs in mammals• Enclosed, protected by ribs
Gas Exchange Systems
• Lungs• Thin, delicate
membrane between air and blood
08 April 2015 Gas-Exchange.ppt 12
08 April 2015 Gas-Exchange.ppt 13
Gas Exchange
• To, temperature
• S, solubility
• mol. wt., molecular weight of diffusing gas
• r, rate of diffusion
• P, difference in partial pressure (O2 or CO2)
• A, area of exchange membrane
• d, distance
08 April 2015 Gas-Exchange.ppt 14
Gas Exchange
• Constantso temperature (= body temperature)
o solubility (property of O2 or CO2)
o molecular weight (property of O2 or CO2)
• These don’t change. Disregard.
08 April 2015 Gas-Exchange.ppt 15
Gas Exchange
• r, rate of diffusion
• P, difference in partial pressure (O2 or CO2)
• A, area of exchange membrane
• d, distance
08 April 2015 Gas-Exchange.ppt 16
Gas Exchange
• To maximize diffusion rate:• Maximize P
• Maximize Area
• Minimize distance.
• These result from evolutionary and physiological adaptation.
08 April 2015 Gas-Exchange.ppt 17
Gas Transport
• Ventilation of alveoli
• O2 diffusion from alveoli to hemoglobin in RBC’s • Equilibrium pO2 = 100 mmHg
• Diffusion from hemoglobin to body tissues• Equilibrium pO2 = 40 mmHg
08 April 2015 Gas-Exchange.ppt 18
Gas Transport
• CO2 diffusion from body tissues to hemoglobin• Equilibrium pCO2 = 45 mmHg
• Diffusion from hemoglobin in RBC’s to alveoli• Equilibrium pCO2 = 40 mmHg
• Ventilation of alveoli
08 April 2015 Gas-Exchange.ppt 19
Gas Transport
• Hemoglobin• Oxygen-hemoglobin
dissociation curve
• Hb binds O2 at high pO2
• Hb releases O2 at low pO2
08 April 2015 Gas-Exchange.ppt 20
Gas Transport
• Hemoglobin• Oxygen-hemoglobin
dissociation curve
• Exercise lowers pO2 and pH in muscles, higher temperature
• Hb releases more O2 at low pO2 , low pH, and high temperature
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