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。

They can feel the difference between a conical shaped cell like this and a flat cell.

他们可以感觉到像这样的圆锥形细胞和扁平细胞之间的区别。