Mesoderm 39044 221393066 2008-06-24T09:20:20Z Closedmouth 372693 Reverted edits by [[Special:Contributions/122.2.208.15|122.2.208.15]] to last version by Tycho (using [[WP:HG|Huggle]]) {{Infobox Embryology | Name = {{PAGENAME}} | Latin = | GraySubject = 6 | GrayPage = 49| Image = mesoderm.png | Caption = Organs derived from mesoderm. | Image2 = Gray21.png | Caption2 = Section through the embryo | System = | CarnegieStage = | Days = 16 | Precursor = | GivesRiseTo = | MeshName = Mesoderm | MeshNumber = A16.254.425.660 | DorlandsPre = | DorlandsSuf = | }} The [[germ layer]] '''mesoderm''' forms in the [[embryo]]s of [[animal]]s more complex than [[cnidaria]]ns, making them [[triploblastic]]. Mesoderm forms during [[gastrulation]] when some of the cells migrating inward to form the [[endoderm]] form an additional layer between the endoderm and the [[ectoderm]]. This key innovation evolved hundreds of millions of years ago and led to the evolution of nearly all large, complex animals. The formation of a mesoderm led to the formation of a [[body cavity|coelom]]. Organs formed inside a coelom (body cavity) can freely move, grow, and develop independently of the body wall while fluid cushions and protects them from shocks. ==Categorizing animals== Not all triploblastic animals have a coelom, like the simplest animals with organs that form from three tissue layers: [[flatworm]]s. Three different configurations of mesoderm in relation to ectoderm form a method of categorizing animals. *'''Acoelomates''' **no coelom **tissues and organs packed between gut and body wall *'''Pseudocoelomates''' **false coelom **unlined or partially lined body cavity between gut and body wall *'''Coelomates''' **proper coelom **lined cavity between gut and body wall ==Derivatives== ===General=== Note: Not all triploblasts produce all of the items listed. *[[skeletal system|bones]] *most of the [[circulatory system]], including the [[heart]] and major blood vessels *[[connective tissue]]s of the gut and [[integumentary system|integuments]] *[[mesenchyme]] *[[mesothelium]] *[[muscular system|muscles]] *[[peritoneum]] (lining of the coelom) *[[reproductive system]] *[[urinary system]], including the [[kidney]]s ===Vertebrates=== [[Image:Image19.png|thumb|350px|Transverse section of a chick embryo of forty-five hours' incubation.<br/> * ''Chordamesoderm:'' yellow, at the [[notochord]].<br/> * ''Paraxial mesoderm:'' red, comprising the [[somite]]s.<br/> * ''Intermediate mesoderm:'' purple, which includes the [[Wolffian duct]].<br/> * ''Lateral plate mesoderm:'' purple, comprising somatic and splanchic mesoderm.]] In addition to the general list, the mesoderm of a developing vertebrate differentiates into the following: * [[Chordamesoderm]] * [[Paraxial mesoderm]] * [[Intermediate mesoderm]] * [[Lateral plate mesoderm]] ==See also== *[[Ectoderm]] *[[Endoderm]] *[[Germ layer]] *[[Histogenesis]] *[[Organogenesis]] ==Additional images== <gallery> Image:Gray32.png|Section through ovum imbedded in the uterine decidua Image:Gray35.png|Transverse section of a chorionic villus. Image:Gray36.png|Primary chorionic villi. Diagrammatic. Image:Gray37.png|Secondary chorionic villi. Diagrammatic. </gallery> ==References== {{wiktionary|mesoderm}} *Evers, Christine A., Lisa Starr. ''Biology:Concepts and Applications.'' 6th ed. United States:Thomson, 2006. ISBN 0-534-46224-3. ==External links== * {{EmbryologyUNSW|Notes/skmus6}} * {{EmbryologyTemple|EMBIII97/sld039}} {{Embryology}} {{Germ layer}} [[Category:Developmental biology]] [[Category:Embryology]] [[Category:Gastrulation]] [[ar:أديم متوسط]] [[cs:Mezoderm]] [[da:Mesoderm]] [[de:Mesoderm]] [[es:Mesodermo]] [[eo:Mezodermo]] [[fr:Mésoderme]] [[it:Mesoderma]] [[lt:Mezoderma]] [[nl:Mesoderm]] [[pl:Mezoderma]] [[pt:Mesoderme]] [[fi:Mesodermi]] [[sv:Mesoderm]] [[tr:Mezoderm]] [[uk:Мезодерма]] [[zh:中胚层]]