Final answer:
The partial pressure of oxygen in the blood is indeed lower than in the exhaled medium during exhalation, which is due to the gas exchange process based on pressure gradients in the alveoli and the blood. The correct option is C).
Step-by-step explanation:
Yes, the partial pressure of oxygen is lower in the blood compared to the exhaled medium during exhalation. This is because during tidal flow, external respiration involves gas exchange where oxygen diffuses from the alveoli into the blood due to a pressure gradient.
Oxygen in the alveoli has a partial pressure of about 150 mm Hg, while the partial pressure of oxygen in the oxygenated blood is about 100 mm Hg. During exhalation, the blood's partial pressure of oxygen remains lower than the oxygen in the exhaled air, which still contains a significant amount of oxygen not absorbed by the lungs.
Gas exchange removes oxygen from and adds carbon dioxide to alveolar air, with both deep and forced breathing causing changes in the alveolar air composition more rapidly than during quiet breathing.
This affects the diffusion process that moves these gases across the respiratory membrane. Oxygen enters and carbon dioxide leaves the blood based on their respective partial pressures.
Therefore, the answer to the question is C) Yes, during exhalation, since the blood's partial pressure of oxygen, after gas exchange, is lower than that in the exhaled air.