What is a "membrane"?

A membrane refers to a thin, flexible layer of tissue that covers, lines, or separates various structures and organs. These membranes serve diverse functions, such as protecting organs, providing structural support, facilitating movement and flexibility, and allowing for the exchange of substances. Examples of membranes in the human body include the mucous membranes that line the respiratory and digestive tracts, the serous membranes that encase organs in protective fluid-filled cavities, and the cell membranes that surround individual cells, regulating the passage of molecules. Membranes are essential for the proper functioning and integration of different body systems.