A coelom is a fluid-filled body cavity completely lined by mesodermal tissue. It provides space for the development and suspension of internal organs and contributes to the complexity of animal body plans.
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Coeloms allow for the development of more complex organ systems compared to acoelomates.
Animals with a true coelom are called coelomates, whereas those without it are termed acoelomates or pseudocoelomates.
The presence or absence of a coelom is an important characteristic in animal classification.
In coelomates, the coelom can develop through two processes: schizocoely (splitting within the mesoderm) or enterocoely (outpocketing of the gut).
Examples of coelomate animals include annelids, mollusks, arthropods, echinoderms, and chordates.
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Related terms
Acoelomate: An animal that lacks a fluid-filled body cavity.
Pseudocoelomate: An animal with a body cavity that is not entirely lined by mesodermal tissue.
Mesoderm: The middle layer of embryonic tissue that develops into muscles, bones, and other organs in triploblastic animals.