通常细胞外层的皮肤也不断下跌，并代之以新的细胞，这种细胞所产生的基底层。

Normally the cells of the outer layer of the skin are constantly shed and replaced by new cells, which are produced by the basal layers.

youdao

他们发现在皮肤表面生长的普通细菌可以通过释放一种特殊的分子阻止外层细胞发炎来帮助伤口复合。

They found common bacteria living on the surface of skin that can help wounds to heal by releasing a special molecule to stop outer-skin cells getting inflamed.

youdao

薄膜内层间隙足够小，细胞不会渗漏出去。膜的外层间隙足够大，血管能沿着膜面生长。

The inner layer of the membrane is small enough to prevent the cells from leaking out, but the outer layer is large enough to encourage blood vessels to grow along the membrane.

youdao

These cells around the outside form the interface, the placenta, where the maternal blood circulation meets the embryonic circulation and nutrients are passed back and forth that way in a very highly regulated and important way.

外层的细胞形成接触面,即胎盘,是母血与胎血,进行血液交换,及营养物质交换的场所,整个过程高度有序并且非常重要

耶鲁公开课 - 生物医学工程探索课程节选