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Lecture 5. Gas Exchange
• cellular respiration, oxidative processes within cells
• external respiration, exchange of O2 and CO2 between the organism and its environment
Gas Exchange Surfaces
• for diffusion to be effective, gas-exchange regions must be:– moist– thin– relatively large
• effectiveness of diffusion is enhanced by vascularization
• cutaneous respiration (direct diffusion)
Respiratory Organs
Respiratory Organs
• Tracheal systems (branching system of tubes)
Respiratory Organs
• Gills or branchia (external or internal)
papulae (dermal branchiae or skin gills)
Respiratory Organs
• Gills or branchia (external or internal)
branchial tufts (gills) in marine worm
gills in axolotl (Ambystoma mexicanum)
Respiratory Organs
• Gills or branchia (external or internal)
parapodia in ragworm (Nereis spp.)
Respiratory Organs
• Gills or branchia (external or internal)
How a fish ventilates its gills
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
countercurrent flow/exchange
Respiratory Organs
• Lungs (invaginations)
A frog ventilates its lungs by positive pressure breathing.
• Lungs of frogs
• Lungs of mammals
Mammals ventilate their lungs by negative pressure breathing.
• Lungs of mammals
• Lungs of birds
http://www.peteducation.com/article.cfm?c=15+1829&aid=2721
• Lungs of birds
http://www.peteducation.com/article.cfm?c=15+1829&aid=2721
• the volume of air an animal inhales and exhales with each breath is called tidal volume– it averages about 500 mL in resting humans
• the maximum tidal volume during forced breathing is the vital capacity– about 3.4 L and 4.8 L for college-age females and
males, respectively
• most animals transport most of the O2 bound to special proteins called respiratory pigments– hemocyanin– hemoglobin
• when the control center registers a slight drop in pH, it increases the depth and rate of breathing, and the excess CO2 is eliminated in exhaled air
• O2 diffuses into pulmonary capillaries
• most O2 combines with hemoglobin in red blood cells to form oxyhemoglobin
• CO2 diffuses out of pulmonary capillaries
• most CO2 is transported in the form of bicarbonate ion
• some CO2 combines with hemoglobin to form carbaminohemoglobin
Fig. 31.27
• cooperative oxygen binding and release is evident in the dissociation curve for hemoglobin
• a drop in pH lowers the affinity of hemoglobin for O2, an effect called the Bohr shift
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