What is the main mechanism for the exchange of O₂ and CO₂ in the...

Exchange of O₂ and CO₂ at the alveoli and tissues occur by diffusion. Rate of diffusion is dependent on the partial pressure gradients of O₂ (pO₂) and CO₂ (pCO₂), their solubility as well as the thickness of the diffusion surface. Alveoli are the primary sites of exchange of gases. Exchange of gases also occur between blood and tissues. O₂ and CO₂ are exchanged in these sites by simple diffusion mainly based on pressure/concentration gradient. Solubility of the gases as well as the thickness of the membranes involved in diffusion are also some important factors that can affect the rate of diffusion.