The mesohyl, formerly known as

mesenchyme Mesenchyme () is a type of loosely organized animal embryonic connective tissue of undifferentiated cells that give rise to most tissues, such as skin, blood or bone. The interactions between mesenchyme and epithelium help to form nearly every o ...

or as

mesoglea Mesoglea refers to the extracellular matrix found in cnidarians like coral or jellyfish that functions as a hydrostatic skeleton. It is related to but distinct from mesohyl, which generally refers to extracellular material found in sponges. Desc ...

, is the gelatinous matrix within a

sponge Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through t ...

. 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 in other animals. Structure The pinacoderm is composed of pinacocytes, flattened epithelial cells that can ...

and the internal

choanoderm The choanoderm is a type of cell layer composed of flagellated collar cells, or choanocytes, found in sponges. The sponge body is mostly a connective tissue; the mesohyl, over which are applied epithelioid monolayers of cells, the outer pinacoder ...

. The mesohyl resembles a type of

connective tissue Connective tissue is one of the four primary types of animal tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Connective tiss ...

and contains several amoeboid cells such as amebocytes, as well as

fibrils Fibrils (from the Latin ''fibra'') are structural biological materials found in nearly all living organisms. Not to be confused with fibers or filaments, fibrils tend to have diameters ranging from 10-100 nanometers (whereas fibers are micro ...

and

skeletal A skeleton is the structural frame that supports the body of an animal. There are several types of skeletons, including the exoskeleton, which is the stable outer shell of an organism, the endoskeleton, which forms the support structure inside ...

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

layers are tissues. The mesohyl is composed of the following main elements:

collagen Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whole ...

, fibronectin-like molecules,

galectin Galectins are a class of proteins that bind specifically to β-galactoside sugars, such as ''N''-acetyllactosamine (Galβ1-3GlcNAc or Galβ1-4GlcNAc), which can be bound to proteins by either N-linked or O-linked glycosylation. They are also t ...

, and a minor component,

dermatopontin Dermatopontin also known as tyrosine-rich acidic matrix protein (TRAMP) is a protein that in humans is encoded by the ''DPT'' gene. Dermatopontin is a 22-kDa protein of the noncollagenous extracellular matrix (ECM) estimated to comprise 12 mg ...

. These

polypeptides Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. A p ...

form the

extracellular matrix In biology, the extracellular matrix (ECM), also called intercellular matrix, is a three-dimensional network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide stru ...

which provides the platform for specific

cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery ...

adhesion as well as for

signal In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The '' IEEE Transactions on Signal Processing' ...

transduction and

cellular growth Cell growth refers to an increase in the total mass of a cell, including both cytoplasmic, nuclear and organelle volume. Cell growth occurs when the overall rate of cellular biosynthesis (production of biomolecules or anabolism) is greater than t ...

. The mesohyl includes a noncellular colloidal

with embedded collagen fibers, spicules and various cells, being as such a type of

.Brusca, R.C. & Brusca, G.J. (2003). ''Invertebrates''. 2nd ed. Sunderland, Massachusetts: Sinauer Associates, p. 183.

References

Bibliography

* * Sponge anatomy {{sponge-stub