Membranes that line many internal organs and cavities, secreting a thin, lymph-like fluid, that lubricates and slowly circulates.
These are smooth, transparent membranes that line certain large cavities of the body. The chief serous membranes are the PERITONEUM, lining the cavity of the abdomen; the pleurae (see PLEURA), one of which lines each side of the chest, surrounding the corresponding lung; the PERICARDIUM, in which the heart lies; and the tunica vaginalis on each side, enclosing a testicle. The name of these membranes is derived from the fact that the surface is moistened by thin ?uid derived from the serum of blood or LYMPH. Every serous membrane consists of a visceral portion, which closely envelops the organs concerned, and a parietal portion, which adheres to the wall of the cavity. These two portions are continuous with one another so as to form a closed sac, and the opposing surfaces are close together, separated only by a little ?uid. This arrangement enables the organs in question to move freely within the cavities containing them. For further details, see under PERITONEUM.
The mucus-secreting skin that lines (and protects against the environment) all openings, cavities or entrances into the body, such as the intestinal tract, lungs, urinary tract, sinuses, vagina, etc.... mucous membranes (mucosa)
the membranous structures that surround the embryo and contribute to the placenta and umbilical cord. They include the *amnion, *chorion, *allantois, and *yolk sac. In humans the allantois is always very small and by the end of pregnancy the amnion and chorion have fused into a single membrane and the yolk sac has disappeared.... extraembryonic membranes
(serosa) a smooth transparent membrane, consisting of *mesothelium and underlying elastic fibrous connective tissue, lining certain large cavities of the body. The *peritoneum of the abdomen, *pleura of the chest, and *pericardium of the heart are all serous membranes. Each consists of two portions: the parietal portion lines the walls of the cavity, and the visceral portion covers the organs concerned. The two are continuous, forming a closed sac with the organs essentially outside the sac. The inner surface of the sac is moistened by a thin fluid derived from blood serum, which allows frictionless movement of organs within their cavities. Compare mucous membrane.... serous membrane
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