Mesothelium
Encyclopedia
The mesothelium is a membrane that forms the lining of several body cavities: the pleura (thoracic 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.
It is a form of simple squamous epithelium
.
nic mesoderm cell layer, that lines the 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.
supported by Dense irregular connective tissue
. Cuboidal mesothelial cells may be found at areas of injury, the milky spots of the omentum
, and the peritoneal side of the 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.
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.
Peritoneum
The peritoneum is the serous membrane that forms the lining of the abdominal cavity or the coelom — it covers most of the intra-abdominal organs — in amniotes and some invertebrates...
(abdominal cavity including the mesentery
Mesentery
In anatomy, the mesentery is the double layer of peritoneum that suspends the jejunum and ileum from the posterior wall of the abdomen. Its meaning, however, is frequently extended to include double layers of peritoneum connecting various components of the abdominal cavity.-Mesentery :The...
) and pericardium
Pericardium
The pericardium is a double-walled sac that contains the heart and the roots of the great vessels.-Layers:...
(heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
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
Perimetrium
The perimetrium is the outer serosa layer of the uterus, equivalent to peritoneum.-External links: - "The Female Pelvis: The uterus" - "Mammal, uterus "...
). Mesothelium that covers the internal organs is called visceral mesothelium, while the layer that covers the body walls is called the parietal
Parietal
Parietal may refer to:*Parietal placentation*Parietal lobe of the brain*Parietal bone of the skull*Parietal scales of a snake lie in the general region of the parietal bone*Parietal cell in the stomach*Parietal pleura...
mesothelium.
It is a form of simple squamous epithelium
Simple squamous epithelium
A simple squamous epithelium is a single layer of flat cells in contact with the basal lamina of the epithelium. This type of epithelium is often permeable and occurs where small molecules pass quickly through membranes via filtration or diffusion...
.
Origin
Mesothelium derives from the embryoEmbryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
nic mesoderm cell layer, that lines the coelom
Body cavity
By the broadest definition, a body cavity is any fluid-filled space in a multicellular organism. However, the term usually refers to the space located between an animal’s outer covering and the outer lining of the gut cavity, where internal organs develop...
(body cavity) in the embryo. It develops into the layer of cells that covers and protects most of the internal organs of the body.
Structure
The mesothelium forms a monolayer of flattened squamous-like epithelial cells resting on a thin basement membraneBasement membrane
The basement membrane is a thin sheet of fibers that underlies the epithelium, which lines the cavities and surfaces of organs including skin, or the endothelium, which lines the interior surface of blood vessels.- Composition :...
supported by Dense irregular connective tissue
Dense irregular connective tissue
Dense irregular connective tissue has fibers that are not arranged in parallel bundles as in dense regular connective tissue.-Substances formed:...
. Cuboidal mesothelial cells may be found at areas of injury, the milky spots of the omentum
Omentum
Omentum may refer to:* greater omentum* lesser omentum...
, and the peritoneal side of the diaphragm
Thoracic diaphragm
In the anatomy of mammals, the thoracic diaphragm, or simply the diaphragm , is a sheet of internal skeletal muscle that extends across the bottom of the rib cage. The diaphragm separates the thoracic cavity from the abdominal cavity and performs an important function in respiration...
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
Extracellular matrix
In biology, the extracellular matrix is the extracellular part of animal tissue that usually provides structural support to the animal cells in addition to performing various other important functions. The extracellular matrix is the defining feature of connective tissue in animals.Extracellular...
proteins to aid in serosal repair, and the release of factors to promote the disposition and clearance of fibrin
Fibrin
Fibrin is a fibrous, non-globular protein involved in the clotting of blood. It is a fibrillar protein that is polymerised to form a "mesh" that forms a hemostatic plug or clot over a wound site....
(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
- MesotheliomaMesotheliomaMesothelioma, more precisely malignant mesothelioma, is a rare form of cancer that develops from the protective lining that covers many of the body's internal organs, the mesothelium...
: (cancerCancerCancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
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 asbestosAsbestosAsbestos is a set of six naturally occurring silicate minerals used commercially for their desirable physical properties. They all have in common their eponymous, asbestiform habit: long, thin fibrous crystals...
exposure.
- Intra-abdominal adhesions: Normally, the mesothelium secretes plasminogen, which removes fibrinFibrinFibrin is a fibrous, non-globular protein involved in the clotting of blood. It is a fibrillar protein that is polymerised to form a "mesh" that forms a hemostatic plug or clot over a wound site....
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 dialysisPeritoneal dialysisPeritoneal dialysis is a treatment for patients with severe chronic kidney disease. The process uses the patient's peritoneum in the abdomen as a membrane across which fluids and dissolved substances are exchanged from the blood...
patients. The presence of supra-physiological glucose concentrations, acidity, and glucose degradation products in peritoneal dialysis fluids contribute to the fibrosisFibrosisFibrosis is the formation of excess fibrous connective tissue in an organ or tissue in a reparative or reactive process. This is as opposed to formation of fibrous tissue as a normal constituent of an organ or tissue...
of the peritoneal mesothelium, either by epithelial-mesenchymal transitionEpithelial-mesenchymal transitionEpithelial-mesenchymal transition or transformation is a hypothesized program of development of biological cells characterized by loss of cell adhesion, repression of E-cadherin expression, and increased cell mobility...
or increased proliferation of existing fibroblasts. A fibrosed peritoneum results in the increased passage of solutes across the peritoneum and ultrafiltration failure.
External links
- Mesothelioma: Questions and Answers (National Cancer InstituteNational Cancer InstituteThe National Cancer Institute is part of the National Institutes of Health , which is one of 11 agencies that are part of the U.S. Department of Health and Human Services. The NCI coordinates the U.S...
). "Mesothelium" - "Tissues, Layers, and Organs: transverse section of rat gut"