覆盖物
... layer 层 integument (指天然的)覆盖物... heel 脚后跟 ...
In biology, integument is the natural covering of an organism or an organ, such as its skin, husk, shell, or rind.It derives from integumentum, which means "a covering" in Latin. In a transferred or figurative sense, it could mean a cloak or a disguise. In English "integument" is a fairly modern word, its origin having been traced back to the early seventeenth century. It can mean a material or layer with which anything is enclosed, clothed, or covered in the sense of "clad" or "coated", as with a skin or husk.