Mesoderm
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2008-06-24T09:20:20Z
Closedmouth
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Reverted edits by [[Special:Contributions/122.2.208.15|122.2.208.15]] to last version by Tycho (using [[WP:HG|Huggle]])
{{Infobox Embryology |
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Image = mesoderm.png |
Caption = Organs derived from mesoderm. |
Image2 = Gray21.png |
Caption2 = Section through the embryo |
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CarnegieStage = |
Days = 16 |
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MeshName = Mesoderm |
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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]]
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