The mesohyl, formerly known as
mesenchyme or as
mesoglea, is the gelatinous matrix within a
sponge. It fills the space between the external
pinacoderm The pinacoderm is the outermost layer of body cells (pinacocytes) of organisms of the phylum Porifera (sponges), equivalent to the Epidermis (skin), epidermis in other animals.
Structure
The pinacoderm is composed of pinacocytes, flattened epitheli ...
and the internal
choanoderm. The mesohyl resembles a type of
connective tissue
Connective tissue is one of the four primary types of animal tissue, a group of cells that are similar in structure, along with epithelial tissue, muscle tissue, and nervous tissue. It develops mostly from the mesenchyme, derived from the mesod ...
and contains several
amoeboid cells such as
amebocytes, as well as
fibrils and
skeletal elements.
For a long time, it has been largely accepted that sponges lack true
tissue, but it is currently debated as to whether mesohyl and
pinacoderm The pinacoderm is the outermost layer of body cells (pinacocytes) of organisms of the phylum Porifera (sponges), equivalent to the Epidermis (skin), epidermis in other animals.
Structure
The pinacoderm is composed of pinacocytes, flattened epitheli ...
layers are tissues.
The mesohyl is composed of the following main elements:
collagen
Collagen () is the main structural protein in the extracellular matrix of the connective tissues of many animals. It is the most abundant protein in mammals, making up 25% to 35% of protein content. Amino acids are bound together to form a trip ...
, fibronectin-like molecules,
galectin, and a minor component,
dermatopontin. These
polypeptides form the
extracellular matrix which provides the platform for specific
cell adhesion as well as for
signal
A signal is both the process and the result of transmission of data over some media accomplished by embedding some variation. Signals are important in multiple subject fields including signal processing, information theory and biology.
In ...
transduction and
cellular growth.
The mesohyl includes a noncellular colloidal
mesoglea with embedded collagen fibers, spicules and various cells, being as such a type of
mesenchyme.
[Brusca, R.C. & Brusca, G.J. (2003). ''Invertebrates''. 2nd ed. Sunderland, Massachusetts: Sinauer Associates, p. 183.]
References
Bibliography
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Sponge anatomy
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