These are very deep lesions that go not just on the surface of your skin like a blister would, but down into the dermis or deeper layers of the skins, as well.

这些伤非常深,它们不仅像水泡那样存在于皮肤表面,还深入到真皮层或者皮下更深的地方

耶鲁公开课 - 生物医学工程探索课程节选