coelom

(noun)

a fluid-filled cavity within the body of an animal; the digestive system is suspended within the cavity, which is lined by a tissue called the peritoneum

Related Terms

Examples of coelom in the following topics:

  • Animal Characterization Based on Features of Embryological Development

    • Triploblasts can be differentiated into three categories: those that do not develop an internal body cavity called a coelom (acoelomates), those with a true coelom (eucoelomates), and those with "false" coeloms (pseudocoelomates) .
    • Eucoelomates (or coelomates) have a true coelom that arises entirely within the mesoderm germ layer and is lined by an epithelial membrane.
    • Although still functional, these are considered false coeloms.
    • The coelom of most protostomes is formed through a process called schizocoely, when a solid mass of the mesoderm splits apart and forms the hollow opening of the coelom.
    • These pouches eventually fuse to form the mesoderm, which then gives rise to the coelom.

  • Superphylum Ecdysozoa

    • The other idea about the phylogeny of the Ecdysozoa is called the coelomate hypothesis.
    • There were three types, or grades, of organization: the Acoelomata (no coelom), the Pseudocoelomata (partial coelom), and the Eucoelomata (true coelom).
    • With the introduction of molecular phylogenetics, the coelomate hypothesis was abandoned, although some molecular, phylogenetic support for the Coelomata continued until 2005.

  • Types of Skeletal Systems

    • A hydrostatic skeleton is one formed by a fluid-filled compartment within the body: the coelom.
    • The organs of the coelom are supported by the aqueous fluid, which also resists external compression.
    • Movement in a hydrostatic skeleton is provided by muscles that surround the coelom.
    • The muscles in a hydrostatic skeleton contract to change the shape of the coelom; the pressure of the fluid in the coelom produces movement.

  • Phylum Annelida

    • Annelids include segmented worms, such as leeches and earthworms; they are the most advanced worms as they possess a true coelom.
    • Annelids show the presence of a true coelom, derived from embryonic mesoderm and protostomy.
    • Each segment is limited by a membranous septum that divides the coelomic cavity into a series of compartments.
    • Additionally, the segmentation of the body wall may not correspond to the internal segmentation of the coelomic cavity.

  • Superphylum Lophotrochozoa

    • This layer multiplies into a band which then splits internally to form the coelom; this protostomic coelom is termed schizocoelom.

  • Skin, Gills, and Tracheal Systems

    • In animals that contain coelomic fluid instead of blood, oxygen diffuses across the gill surfaces into the coelomic fluid.

  • The Evolution of Reproduction

    • These organisms produce sperm and eggs from undifferentiated cells in their coelom, storing them in that cavity.
    • When the coelom becomes filled, the cells are released through an excretory opening or by the body splitting open.
    • These types of reproductive systems developed in insects (compared to annelids which have a coelom for storage).

  • Phylum Platyhelminthes

    • The Platyhelminthes are flatworms that lack a coelom; many are parasitic; all lack either a circulatory or respiratory system.

  • Phylum Nemertea

    • The circulatory system is derived from the coelomic cavity of the embryo.
    • Although these are called blood vessels, since they are of coelomic origin, the circulatory fluid is colorless.

  • Phylum Mollusca

    • The mantle cavity develops independently of the coelomic cavity.