membranous

adjective3

1. •
   made of or like a very thin, soft layer that is easy to bend, such as the skin inside the shell of an egg
2. •
   Thin, pliable, and often transparent.

   • The microcannon starts with a membranous polymer film. — 2016
3. •
   (of a disease) in which a thin layer of tissue forms in the body, usually where no such layer belongs