被覆于机体表面，直接与外界环境相接触的器官。
The organ that is covered on the surface of the body and directly in contact with the external environment.

包裹香囊的外层皮膜或外皮。
The outer skin or membrane that encloses the scent gland sac.

皮肤表面分泌的粘液或黏液层。
Mucus secreted on the skin surface.