Pinacocytes are flat cells found on the outside of

sponges Sponges or sea sponges are primarily marine invertebrates of the animal phylum Porifera (; meaning 'pore bearer'), a basal clade and a sister taxon of the diploblasts. They are sessile filter feeders that are bound to the seabed, and ar ...

, as well as the internal canals of a sponge. Pinacocytes are not specific to the sponge however. It was discovered that pinacocytes do not have as many sponge specific genes. These genes suggest that pinacocytes had evolved before the

metazoan Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia (). With few exceptions, animals consume organic material, breathe oxygen, have myocytes and are able to move, can reproduce sexually, and grow from a ho ...

time period, which is, before porifera had evolved.

Function

Pinacocytes are part of the

epithelium Epithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial ( mesothelial) tissues line the outer surfaces of man ...

in sponges. They play a role in movement (contracting and stretching), cell adhesion, signaling, phagocytosis, and polarity. Pinacocytes are filled with mesohyl which is a gel like substance that helps maintain the shape and structure of the sponge.

Types

Basipinacocytes

These are the cells in contact with the sponge's substrate (the surface to which it is attached).

Exopinacocytes

These are found on the exterior of the sponge. Exopinococytes produce spicules which is a needle like process that serves as structure for the organism.

Endopinacocytes

These line the sponge's interior canals.

References

Cells Sponge anatomy {{poriferan-stub