n. [ F., fr. L. membrana the skin that covers the separate members of the body, fr. L. membrum. See Member. ] (Anat.) A thin layer or fold of tissue, usually supported by a fibrous network, serving to cover or line some part or organ, and often secreting or absorbing certain fluids. [ 1913 Webster ]

☞ The term is also often applied to the thin, expanded parts, of various texture, both in animals and vegetables. [ 1913 Webster ]

Adventitious membrane, a membrane connecting parts not usually connected, or of a different texture from the ordinary connection; as, the membrane of a cicatrix. --
Jacob's membrane. See under Retina. --
Mucous membranes (Anat.), the membranes lining passages and cavities which communicate with the exterior, as well as ducts and receptacles of secretion, and habitually secreting mucus. --
Schneiderian membrane. (Anat.) See Schneiderian. --
Serous membranes (Anat.) , the membranes, like the peritoneum and pleura, which line, or lie in, cavities having no obvious outlet, and secrete a serous fluid. [ 1913 Webster ]

a. [ L. membraneus of parchment. ] See Membranous. [ 1913 Webster ]