Mesothelium 315175 215445662 2008-05-28T06:27:01Z 161.225.129.111 The '''mesothelium''' is a membrane that forms the lining of several body cavities: the [[pleura]] (thoracal cavity), [[peritoneum]] (abdominal cavity including the mesentery) and [[pericardium]] (heart sac). Mesothelial tissue also surrounds the male internal reproductive organs (the [[tunica vaginalis testis]]) and covers the internal reproductive organs of women (the [[tunica serosa uteri]]). Mesothelium that covers the internal organs is called [[visceral]] mesothelium, while the layer that covers the body walls is called the [[parietal]] mesothelium. ==Origin== Mesothelium derives from the [[embryo]]nic [[Germ layer#Mesoderm|mesoderm]] cell layer, that lines the [[body cavity| coelom]] (body cavity) in the embryo. It develops into the layer of cells that covers and protects most of the internal organs of the body. [[Image:L12 IL-1 48hr 0ng.JPG|thumbnail|right|A layer of mesothelial cells grown in [[cell culture]], featuring the typical "[[cobblestone]]" appearance]] == Structure == The mesothelium forms a monolayer of flattened [[squamous]]-like [[epithelial]] cells resting on a thin [[basement membrane]] supported by [[connective tissue]]. [[Cuboidal]] mesothelial cells may be found at areas of injury, the milky spots of the [[omentum]], and the [[peritoneal]] side of the [[Thoracic diaphragm|diaphragm]] overlaying the [[lymphatic]] [[lacunae]]. The luminal surface is covered with [[microvilli]]. The proteins and serosal fluid trapped by the microvilli provide a frictionless surface for internal organs to slide past one another. ==Function== The mesothelium is composed of an extensive monolayer of specialized cells (mesothelial cells) that line the body's serous cavities and internal organs. The main purpose of these cells is to produce a lubricating fluid that is released between layers, providing a slippery, non-adhesive and protective surface to facilitate intracoelomic movement. The mesothelium is also implicated in the transport and movement of fluid and particulate matter across the serosal cavities, [[leukocyte]] migration in response to inflammatory mediators, synthesis of pro-inflammatory [[cytokines]], [[growth factors]] and [[extracellular matrix]] proteins to aid in serosal repair, and the release of factors to promote the disposition and clearance of [[fibrin]] (such as [[plasminogen]]). It is an [[antigen presenting cell]]. Furthermore, the secretion of [[glycosaminoglycans]] and lubricants may protect the body against infection and tumor dissemination. ==Role in disease== * '''[[Mesothelioma]]:''' ([[cancer]] of the mesothelium) is a disease in which cells of the mesothelium become abnormal and divide without control or order. They can invade and damage nearby tissues and organs. Cancer cells can also metastasize (spread) from their original site to other parts of the body. Most cases of mesothelioma begin in the pleura or peritoneum. More than 90% of mesothelioma cases are linked to [[asbestos]] exposure. * '''Intra-abdominal adhesions:''' Normally, the mesothelium secretes [[plasminogen]], which removes [[fibrin]] deposits. During surgical procedures, the mesothelium may be damaged. Its fibrinolytic capacity becomes insufficient and fibrin accumulates, causing fibrous adhesions between opposing surfaces. These adhesions cause intestinal obstruction and female infertility if it occurs in the abdomen, and may impair cardiac and lung function in the thorax. * '''Ultrafiltration failure:''' The peritoneal mesothelium is implicated in the long-term development of ultrafiltration failure in [[peritoneal dialysis]] patients. The presence of supra-physiological glucose concentrations, acidity, and glucose degradation products in peritoneal dialysis fluids contribute to the [[fibrosis]] of the peritoneal mesothelium, either by [[epithelial-mesenchymal transition]] or increased proliferation of existing [[fibroblasts]]. A fibrosed peritoneum results in the increased passage of solutes across the peritoneum and ultrafiltration failure. ==Sources== * [http://cis.nci.nih.gov/fact/6_36.htm Mesothelioma: Questions and Answers] ([[National Cancer Institute]]). * {{KansasHistology|epithel|epith01}} "Mesothelium" * {{BUHistology|00102loa}} - "Tissues, Layers, and Organs: transverse section of rat gut" * Mutsaers SE. "Mesothelial cells: Their structure, function, and role in serosal repair." ''Respirology'' 2002; '''7''':171-191 {{Tissue layers}} [[Category:Tissues]] [[fr:Mésothélium]] [[it:Mesotelio]] [[ja:中皮]]