Identify the site involved in the diffusion of gases where the partial pressure of oxygen ( pO₂ ) is 40 mm Hg and the partial pressure of carbon dioxide ( pCO₂ ) is 45 mm Hg .

Step-by-step solution

According to the standard data for partial pressures of respiratory gases during diffusion: In atmospheric air, pO₂ = 159 mm Hg and pCO₂ = 0.3 mm Hg . In alveoli, pO₂ = 104 mm Hg and pCO₂ = 40 mm Hg . In oxygenated blood, pO₂ = 95 mm Hg and pCO₂ = 40 mm Hg . In tissues and deoxygenated blood, pO₂ = 40 mm Hg and pCO₂ = 45 mm Hg . Thus, the site with pO₂ = 40 mm Hg and pCO₂ = 45 mm Hg is the tissues. Answer: Tissues