Whole (Gr. Kelia - Cavity)
The coelom is a body cavity in animals with three germ layers. It is located inside the mesoderm and is lined with mesodermal tissue.
The coelom is formed during the embryonic development of the animal from the middle germ layer - the mesoderm. In this case, the mesoderm cells form the internal lining of the coelom.
The whole plays an important role, providing space for the development of internal organs and organ systems, as well as performing supporting and protective functions. In different groups of animals, the whole can be divided into separate cavities by partitions.
Thus, the coelom is a characteristic feature of the organization of animals with a three-layer embryo, arising from the mesoderm and being important for their internal structure.