coelomic sac

anatomy

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June 11, 2026

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The coelomic sac, or coelom, is a body cavity found in many invertebrate animals. It is formed during embryonic development from the mesoderm, the middle germ layer. In a type of coelomate called a schizocoelomate, this cavity forms through the splitting of mesodermal masses.123

During prenatal development, the mesoderm splits into somatic and splanchnic layers, with the coelom forming in the space between them. This cavity eventually becomes divided into specialized areas, such as the pericardial cavity for the heart, pleural cavities for the lungs, and the peritoneal cavity for abdominal organs. The formation and structure of the coelom are key distinctions between different animal groups.423

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excretion
The coxal glands of aquatic arthropods
…as a small sac, the coelomic sac, which opens into a wider region, the labyrinth, having complex infoldings of its walls. The labyrinth opens either directly into the bladder, as in marine lobsters and crabs, or into a narrow part of the tubule, the canal, which in turn opens into…
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…as a small sac, the coelomic sac, which opens into a wider region, the labyrinth, having complex infoldings of its walls. The labyrinth opens either directly into the bladder, as in marine lobsters and crabs, or into a narrow part of the tubule, the canal, which in turn opens into…
Read More