Alveoli in the human lungs are structurally adapted to maximise the rate of gas exchange by diffusion through features such as large surface area, thin walls, rich blood supply, moist lining, and elastic fibres.

Caveats

• Elastic fibres primarily serve a mechanical/ventilatory function (passive recoil for expiration), not a direct diffusion-maximising role; their contribution to gas exchange is indirect, through maintaining alveolar structural integrity and surface area geometry.
• The moist lining's primary function is surfactant-mediated surface tension reduction to prevent alveolar collapse; its role in dissolving gases for diffusion is a secondary effect that the claim does not distinguish.
• Surface area estimates for alveoli vary significantly across sources (~70 m² to ~140 m²) due to differences in measurement methodology, but all sources agree the area is very large — the claim's qualitative characterisation remains valid.