The respiratory membrane separates the alveolar air on one side from the blood on the other.

呼吸膜将一侧的肺泡空气与另一侧的血液分离。

As you can see below, small capillaries press up against the respiratory zone, bringing the blood close to the alveolar air.

正如你在下面所看到的，小毛细血管挤压着紧贴呼吸区，携带血液紧靠肺泡气。

The partial pressure of oxygen is 100 mmHg in alveolar air compared to only 40 mmHg in the blood entering the lungs.

肺泡空气中的氧分压为100 mmHg，而进入肺部的血液中只有40 mmHg。

The partial pressure of carbon dioxide is 40 mmHg in the alveolar air and 45 mmHg in the blood entering the lungs.

肺泡空气中的二氧化碳分压为40 mmHg，进入肺部的血液中的二氧化碳分压为45 mmHg。

As you can see in the picture above, the partial pressure of carbon dioxide in the alveolar air is about 40 mmHg.

如上图所示，肺泡空气中二氧化碳的分压约为40 mmHg。

As you can see, oxygen moves out of the alveolar air into the blood, and carbon dioxide moves out of the blood into the alveolar air.

正如你看到的，氧气从肺泡气移出进入血液，二氧化碳从血液中移入肺泡气。

Carbon dioxide diffuses in the opposite direction since the partial pressure is greater in the blood entering the lungs than it is in the alveolar air.

二氧化碳向相反方向扩散，因为进入肺部血液中的分压比肺泡空气中的分压大。

As you can see from the image above, oxygen moves out of the alveolar air into the blood, while carbon dioxide moves in the opposite direction.

如上图所示，氧气从肺泡空气进入血液，而二氧化碳则向相反方向移动。

Since the partial pressure of oxygen in the alveolar air is 100 mmHg, so also is the partial pressure of oxygen in the blood as it leaves the lungs.

由于肺泡空气中的氧气分压为100 mmHg，因此血液离开肺部时的氧气分压也是如此。