Final answer:
The alveoli of the lungs have the lowest partial pressure of carbon dioxide compared to the blood circulating in systemic arteries and the systemic cells.
Step-by-step explanation:
The alveoli of the lungs have the lowest partial pressure of carbon dioxide compared to the blood circulating in systemic arteries and the systemic cells. The partial pressure of carbon dioxide in the alveoli is about 40 mm Hg, while in the blood of systemic arteries it is around 45 mm Hg. This difference in partial pressure helps facilitate the diffusion of carbon dioxide from the systemic cells into the blood and eventually into the alveoli for removal during exhalation.