当维生素缺乏时，首先会变现在表皮系统（包括毛发和指甲）。

The integumentary system (which includes hair and nails) is often the first place that a serious vitamin deficiency shows up.

youdao

整个建筑是一个复合百叶组成的多层表皮系统，这些百叶可旋转和变厚以适应不同的日照强度、通风要求和材料性能。

The building is a system of multiple layers of composite louvers which thicken and rotate according to solar exposure, ventilation, and materials performance.

youdao

洋葱图经常被用于作为一种视觉类比系统的分析。 你可以看到洋葱的某些表皮信息，然后我们需要去削皮，揭示下面的进一步细节。

you can see certain information on the onion’s skin, and then to get further details we need to peel off the skin and reveal what lies underneath.

youdao

Your stomach is a very complex organ that has a muscle layer, it has an epithelial layer which is the interface with food that comes in, and it also has a nervous system, so does the heart.

你的胃是一个非常复杂的器官,它拥有一个肌肉层,有一个与摄入的食物,相接触的表皮层,也有一套神经系统,心脏也有

耶鲁公开课 - 生物医学工程探索课程节选