The pinacoderm is the outermost layer of body cells (

pinacocytes 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 ...

) of organisms of the phylum

Porifera Sponges or sea sponges are primarily marine invertebrates of the animal phylum Porifera (; meaning 'pore bearer'), a Basal (phylogenetics) , basal clade and a sister taxon of the Eumetazoa , diploblasts. They are sessility (motility) , sessile ...

(sponges), equivalent to the

epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermal layer provides a barrier to infection from environmental pathogens and regulates the ...

in other animals.

Structure

The pinacoderm is composed of

pinacocyte Pinacocytes are flat cells found on the outside of sponges, 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 su ...

s, flattened epithelial cells that can expand or contract to slightly alter the size and shape of the sponge. It also contains

porocytes Porocytes are tubular cells which make up the pores of a sponge known as ostia. Description Covering the sponge is a layer of cells known as the pinacoderm, which is composed of pinacocytes. In a sponge, pinacocytes are a thin, elastic layer whic ...

, oval-shaped cells extending from the pinacoderm to the

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 pinaco ...

(the body layer containing

choanocytes Choanocytes (also known as "collar cells") are cells that line the interior of asconoid, syconoid and leuconoid body types of sponges that contain a central flagellum, or ''cilium,'' surrounded by a collar of microvilli which are connected by ...

References

Sponge anatomy {{animal-anatomy-stub