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Respiratory Membrane and Gas Exchange

In the lungs, gas exchange takes place in the alveolar sacs. Oxygen (O2) diffuses from the alveoli into the capillaries and RBCs. At the same time, carbon dioxide (CO2) in the capillaries diffuses into the alveoli.

Zoom-in image of respiratory membrane
Zoom-in image of respiratory membrane labels: Alveolus and Capillary
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  • The bonding of O2 to hemoglobin in the RBCs causes their color to change from purple to red. See the GIF below
  • During the exchange, the gases must rapidly cross the respiratory membrane that separates the alveolar and capillary lumens.

Gas Exchange

Zoom-in image of respiratory membrane
Zoom-in image of respiratory membrane with labels: Squamous cell
Zoom-in image of respiratory membrane with label: endothelial cell
Zoom-in image of respiratory membrane with label: Basement membrane
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An Overview of Respiratory Membrane and Gas Exchange

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Test yourself with labels: Alveolus, capillary, basement membrane, squamous cell, endothelial cell
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