Hi!
An example of a membrane would be Pericardium. This membrane in particular will cover the heart.
What is the Pericardium?
This membrane is a thin, double layered membrane which protects the heart from injuries as well as external blows.In between the membranes, there is a fluid known as pericardial fluid that is present. The function of this is to also protect the heart.
Hope I could help!
-Peaculiar