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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.
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.
The mesohyl functions as an endoskeleton in most sponges, and is the only skeleton in soft sponges that encrust hard surfaces such as rocks. More commonly the mesohyl is stiffened by mineral spicules , by spongin fibers or both.
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.
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. [3] Types. Basipinacocytes. These are the ...
By cooperatively moving their flagella, choanocytes filter particles out of the water and into the spongocoel, and out through the osculum.This improves both respiratory and digestive functions for the sponge, pulling in oxygen and nutrients and allowing a rapid expulsion of carbon dioxide and other waste products.
In sponges, the mesenchyme is called mesohyl. [25] In diploblasts (Cnidaria and Ctenophora), the mesenchyme is fully ectodermally derived. ... Wikipedia® is a ...