Final answer:
The partial pressure of oxygen (PO₂) in the systemic arterial blood at sea level is about 100 mm Hg, and the partial pressure of carbon dioxide (PCO₂) is around 40 mm Hg.
Step-by-step explanation:
Under resting conditions at sea level, the partial pressure of oxygen (PO₂) in the systemic arterial blood is approximately 100 mm Hg. Meanwhile, the partial pressure of carbon dioxide (PCO₂) is about 40 mm Hg in the systemic arterial blood. The difference in partial pressure drives the exchange of gases, where oxygen diffuses from the alveoli into the blood due to a higher partial pressure in the alveolar air, and carbon dioxide diffuses from the blood into the alveoli since its partial pressure is higher in the blood than the alveolar air.