外层的英文：
exothecium

infantile cortical hyperostosis
【医】婴儿骨外层肥厚症

Between these are fixed precast concrete external cladding panels.
在它们之间填上预制混凝土的外层空心板。

The outer layer of an internal organ or body structure, as of the kidney or adrenal gland.
皮层内部器官或身体结构的外层，如肾或肾上腺皮层

The soft outer wall lining the shell of a tunicate or barnacle.
有膜动物的柔软外皮被囊类动物或藤壶的壳的外层软壁

The outer layer of wallpaper.
壁纸的外层。

The outer layer of a diploblastic animal,such as a jellyfish.
外层双胚层动物的外层，如海蜇

A waterproof plastic skin on a metal sheet
金属板的防水塑料外层.

Biscuits coated with chocolate
外层有巧克力的饼干

Calyx encloses an unopened flower bud
花萼围绕在花瓣外层的一圈。

A parka with a waterproof shell.
具有防水外层的短外套