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The mesohyl, formerly known as mesenchyme or as mesoglea, is the gelatinous matrix within a sponge. It fills the space between the external pinacoderm and the internal choanoderm . The mesohyl resembles a type of connective tissue and contains several amoeboid cells such as amebocytes , as well as fibrils and skeletal elements.
More commonly, the mesohyl is stiffened by mineral spicules, by spongin fibers, or both. 90% of all known sponge species that have the widest range of habitats including all freshwater ones are demosponges that use spongin; many species have silica spicules, whereas some species have calcium carbonate exoskeletons.
Most aspects of sponge biology, including feeding, reproduction, and gas exchange, depend on a low pressure flow of water generated by the flagella of the choanoderm. Three grades of organization, asconoid, syconoid, and leuconoid, reflect the degree of elaboration of the choanoderm layer and mesohyl.
In sponges, the mesenchyme is called mesohyl. [25] In diploblasts (Cnidaria and Ctenophora), the mesenchyme is fully ectodermally derived. ... Wikipedia® is a ...
In order to differentiate the use of the word mesenchyme in vertebrate embryology (that is, undifferentiated tissue found in embryonic true [ento-]mesoderm from which are derived all connective tissues, blood vessels, blood cells, the lymphatic system, and the heart) and the use in invertebrate zoology (a more-or-less solid but loosely organized tissue consisting of a gel matrix [the mesoglea ...
Pinacocytes are filled with mesohyl which is a gel like substance that helps maintain the shape and structure of the sponge. ... Wikipedia® is a registered trademark ...
Repeated cleavage of the zygote egg takes place in the mesohyl and forms a parenchymella larva with a mass of larger internal cells surrounded by small, externally flagellated cells. The resulting swimming larva enters a canal of the central cavity and is expelled with the exhalant current.
The circulation of water brings in food particles and sperm, both of which are collected by choanocytes. In addition to the pinacocyte and choanocyte layers, sponges also have a non-living mesohyl layer that is located between the two living layers. Despite being made up of non-living material, the mesohyl contains living cells called archaeocytes.