Question

At the arterial ends of the pulmonary capillaries_____.

Select the order:
the Po2 is higher in the capillaries than in the alveoli.
the Po2 is lower in the capillaries than in the alveoli.
the Po2 is equal in the capillaries and in the alveoli.
the Po2 is higher at first in the capillaries than in the alveoli, and then it is lower in the alveoli than in the capillaries.

Answer 1

At the arterial ends of the pulmonary capillaries, the Po₂ is lower in the capillaries than in the alveoli. Oxygen diffuses down its pressure gradient from the alveoli into the capillaries, where it binds to hemoglobin.

Step-by-step explanation:

At the arterial ends of the pulmonary capillaries, the Po₂ is lower in the capillaries than in the alveoli.

Oxygen diffuses down its pressure gradient from the alveoli into the capillaries, where it binds to hemoglobin. This creates a strong pressure gradient that allows oxygen to rapidly cross the respiratory membrane and enter the blood in the capillaries. Meanwhile, carbon dioxide diffuses from the blood into the alveoli.