Sclerocytes are specialised cells that secrete the mineralized structures in the body wall of some invertebrates. In

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 ...

s they secrete calcareous or siliceous

spicule Spicules are any of various small needle-like anatomical structures occurring in organisms Spicule may also refer to: *Spicule (sponge), small skeletal elements of sea sponges * Spicule (nematode), reproductive structures found in male nematodes ...

s which are found in the

mesohyl 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 se ...

layer of sponges. The sclerocytes produce spicules via formation of a cellular triad. The triad of cells then undergo

mitosis In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is maint ...

, creating six sclerocytes. In pairs, the sclerocytes secrete the minerals which create the spicules. In

starfish Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea (). Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. Starfish ...

they are present in the

dermis The dermis or corium is a layer of skin between the epidermis (with which it makes up the cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from stress and strain. It is divided i ...

and secrete the calcite microcrystals from which the

ossicles The ossicles (also called auditory ossicles) are three bones in either middle ear that are among the smallest bones in the human body. They serve to transmit sounds from the air to the fluid-filled labyrinth ( cochlea). The absence of the audit ...

are formed. They also function in growth and repair of the ossicles.

References

Sponge anatomy Animal cells {{sponge-stub