The alveolar walls are made of extremely thin flat cells that are surrounded by capillaries.

肺泡壁由被毛细血管包围的极薄的扁平细胞构成。

Together, the alveolar wall and capillaries make a two-cell thick membrane that brings blood and oxygen close enough for diffusion.

肺泡壁和毛细血管一起形成了一个两细胞厚的膜，使血液和氧气足够靠近以进行扩散。

So the alveolar wall, the basement membrane, and the capillary wall is really all that separates the air from the blood, and this is called the blood-gas barrier.

所以，肺泡壁、基底膜和毛细血管壁将空气和血液分离，这个结构叫气血屏障。

The alveolar wall has a completely different structure from the bronchioles - there are no cilia or smooth muscle, and instead the wall is lined by thin epithelial cells called pneumocytes.

肺泡壁与支气管壁结构完全不同，没有纤毛和平滑肌；相反，管壁内有大量薄层上皮细胞，称为肺泡细胞。