Explanation

Partial pressure of $O_{2}$ in alveoli and oxygenated blood are almost same. Alveoli has 104 mm of Hg, whereas oxygenated blood has 95 mm of Hg. Percentage of gases in different parts of body [table] Air Oxygen% Carbon Nitrogen Water dioxide % % vapours ; Inhaled Air 20.84 0.03-0.04 79 Variable Alveolar Air 13.1 5.3 79 Saturated Exhaled Air 15.7 4.0 79.7 Saturated [/table]