Serous membrane 1425177 219012015 2008-06-13T04:41:10Z R.S.(AUA) 7274529 /* External links */ {{Infobox Anatomy |Name = {{PAGENAME}} |Latin = tunica serosa |GraySubject = |GrayPage = |Image = Ens.png |Caption = Layers of the [[enteric nervous system]]. (Serosa at top, in red.) |Image2 = Illu stomach2.jpg |Caption2 = Stomach. (Serosa is labeled at far right, and is colored yellow.) |Precursor = [[mesoderm]] |System = |MeshName = Serous+membrane |MeshNumber = A10.615.789 |DorlandsPre = t_22 |DorlandsSuf = 12832289 }} In [[anatomy]], a '''serous membrane''' (or '''serosa''') is a smooth [[Mesothelium|membrane]] consisting of a thin layer of [[Cell (biology)|cells]] which excrete [[serous fluid]]. Serous membranes line and enclose several body cavities, known as serous cavities, where they secrete a lubricating fluid which reduces friction from muscle movement. Serosa is not to be confused with [[adventitia]], a connective tissue layer which binds together structures rather than reducing friction between them. ==Structure== Each serous membrane is composed of a secretory [[epithelium| epithelial]] layer and a [[connective tissue]] layer underneath. * The ''epithelial layer'', known as [[mesothelium]], consists of a single layer of [[Blood vessel|avascular]] flat [[nucleated]] cells ([[simple squamous epithelium]]) which produce the lubricating serous fluid. This fluid has a consistency similar to thin [[mucus| mucous]]. These cells are bound tightly to the underlying connective tissue. * The ''connective tissue layer'' provides the [[blood vessels]] and [[nerves]] for the overlying secretory cells, and also serves as the binding layer which allows the whole serous membrane to adhere to organs and other structures. For the heart, the surrounding serous membranes include: {| class="wikitable" | '''Outer''' || '''Inner''' |- | Parietal [[peritoneum]] || Visceral peritoneum |- | [[Parietal pleura]] || [[Pulmonary pleura]] |- | Parietal [[pericardium]] || Visceral pericardium ([[epicardium]]) |} Other parts of the body may also have specific names for these structures. For example, the serosa of the [[uterus]] is called the [[perimetrium]]. [[Image:Serous organ invagination.gif|thumb|300px|right|Highly schematic diagram of an organ invaginating into a serous cavity]] The [[pericardium| pericardial cavity]] (surrounding the [[heart]]), [[pleura| pleural cavity]] (surrounding the [[lung]]s) and [[peritoneum| peritoneal cavity]] (surrounding most organs of the [[abdomen]]) are the three serous cavities within the human body. It should be noted that while serous membranes have a lubricative role to play in all three cavities, in the pleural cavity it has a greater role to play in the function of breathing. The serous cavities are formed from the intraembryonic coelom and are basically an empty space within the body surrounded by serous membrane. Early in embryonic life visceral organs develop adjacent to a cavity and invaginate into the bag-like coelom. Therefore each organ becomes surrounded by serous membrane - they ''do not'' lie within the serous cavity. The layer in contact with the organ is known as the visceral layer, while the parietal layer is in contact with the body wall. ==Embryological origins== All serous membranes found in the human body formed ultimately from the [[mesoderm]] of the [[trilaminar embryo]]. The trilaminar embryo consists of three relatively flat layers of [[ectoderm]], [[endoderm]] (also known as "entoderm") and [[mesoderm]]. As the embryo develops, the mesoderm starts to segment into three main regions: the [[paraxial mesoderm]], the [[intermediate mesoderm]] and the [[lateral plate mesoderm]]. The lateral plate mesoderm later splits in half to form two layers bounding a cavity known as the [[intraembryonic coelom]]. Collectively, both layers are known as [[splanchnopleure]]. Individually, each are known as [[visceropleure]] and [[somatopleure]]. * The ''visceropleure'' is associated with the underlying endoderm which it is in contact with, and later becomes the serous membrane in contact with visceral organs within the body. * The ''somatopleure'' is associated with the overlying ectoderm and later becomes the serous membrane in contact with the body wall. The intraembronic coelom can now be seen as a cavity within the body which is covered with serous membrane derived from the splanchnopleure. This cavity is divided and demarcated by the folding and development of the embryo, ultimately forming the serous cavities which house many different organs within the [[thorax]] and [[abdomen]]. ==Additional images== <gallery> Image:Illu stomach layers.jpg|Layers of stomach wall Image:Gray1058.png|Section of duodenum of cat. X 60. </gallery> ==External links== * {{MeshName|serous+membrane}} * {{eMedicineDictionary|serosa}} * {{BUHistology|00102loa}} - "Tissues, Layers, and Organs: transverse section of rat gut" * {{OklahomaHistology|21_02}} - "[[Uterus]]" * {{OklahomaHistology|54_07}} - "[[Jejunum]]" * {{UIUCHistologySubject|844}} {{Tissue layers}} [[Category:Membrane biology]] [[Category:Tissues]] [[de:Tunica serosa]] [[et:Kelme]] [[eo:Serozo]] [[fr:Séreuse]] [[ja:漿膜]] [[pl:Błona surowicza]] [[sv:Serös hinna]] LEGEND FOR ABOVE IMAGE: 1. Serosa 2. Tela subserosa 3. Muscularis 4. Oblique fibers of muscle wall 5. Circular muscle layer 6. Longitudinal muscle layer 7. Submucosa 8. Lamina muscularis mucosae 9. Mucosa 10. Lamina propria 11. Epithelium 12. Gastric glands 13. Gastric pits 14. Villous folds 15. Gastric areas