Coelom
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216967765
2008-06-04T00:52:50Z
122.109.58.162
{{unreferenced|date=April 2008}}
The '''coelom''' (pronounced "seal-um") is a fluid filled cavity formed within the [[mesoderm]]. Coeloms developed in [[triploblast]]s but were subsquently lost in several lineages. Loss of coelom is correlated with reduction in body size. Coeloms are absent in [[diploblastic]] animals such as [[cnidarian]]s.
Functionally, a coelom can absorb shock or provide a [[hydrostatic skeleton]]. It also allows organs to grow independently of the body wall. This can be seen in the digestive tract of earthworms and other [[annelid]]s, which is suspended within the body in a [[mesentery]] derived from a mesoderm-lined coelom. In [[mammals]], the coelom forms the [[peritoneal]], [[pleural]], and [[pericardial sinus|pericardial]] cavities.
In the past, zoologists grouped animals based on characters related to the coelom. The presence or absence of a coelom and the way in which it was formed was believed to be important in understanding the [[phylogenetic]] relationships of animal [[phyla]]. However, recent molecular phylogenies have suggested this characteristics is not as informative as previously believed.
==See also==
*[[Abdominal cavity]]
{{developmental-biology-stub}}
[[Category:Animal anatomy]]
[[Category:Developmental biology]]
[[ca:Celoma]]
[[fr:Cœlome]]
[[it:Celoma]]
[[ja:体腔]]
[[pt:Celoma]]
[[ru:Целом]]
[[sr:Целом]]