Why Does Diffusion Across the Respiratory Membrane Proceed Very Rapidly

Question

Why does diffusion across the respiratory membrane proceed very rapidly?
A) because the gases are lipid-soluble
B) because the distance across the respiratory membrane is short
C) because the basement membrane of the alveolar epithelium is fused with the adjacent capillaries
D) because the the surface area of the blood-air barrier is large
E) All answer choices are correct.

Accepted Answer

All of the answer choices presented contribute to why diffusion across the respiratory membrane proceeds very rapidly. Gases such as O2 and CO2 are lipid-soluble, allowing for them to easily cross the alveolar and capillary membranes. The distance across the respiratory barrier is short, with the alveolar and capillary membranes being approximately 0.5 micrometers apart. The basement membrane of the alveolar epithelium is fused with the adjacent capillaries, eliminating any barriers to diffusion. Lastly, the surface area of the blood-air barrier is large, allowing for a greater amount of gas exchange to occur. Together, these factors allow for efficient and rapid diffusion across the respiratory membrane.