This treatment involves scrubbing off the toplayer of dead skin.
这种治疗需要把死皮的表层除去。
《牛津词典》
2
Because of the cold temperatures, the tundra has two layers: toplayer, which is called the active layer, is frozen in the winter and spring, but thaws in the summer.
由于寒冷的气温，冻土带有两层：最上面的一层被称为活动层，在冬季和春季被冻结，但在夏季解冻。
3
The toplayer of skin has to be grafted onto the burns.