Coenenchyme is the common tissue that surrounds and links the
polyps in
octocorals. It consists of
mesoglea
Mesoglea refers to the extracellular matrix found in cnidarians like coral or jellyfish as well as ctenophores that functions as a hydrostatic skeleton. It is related to but distinct from mesohyl, which generally refers to extracellular material f ...
penetrated by tubes (''solenia'') and canals of the
gastrodermis
Gastrodermis (from Ancient Greek: , , "stomach"; , , "skin") is the inner layer of Cell (biology), cells that serves as a lining membrane of the gastrovascular cavity in cnidarians. It is distinct from the outer epidermis and the inner dermis and ...
and contains
sclerite
A sclerite (Greek language, Greek , ', meaning "hardness, hard") is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instea ...
s, microscopic mineralised
spicules of silica or of calcium carbonate. The outer layer of the coenenchyme is made of columnar or squamous epithelial cells, and can be covered in
microvilli
Microvilli (: microvillus) are microscopic cellular membrane protrusions that increase the surface area for diffusion and minimize any increase in volume, and are involved in a wide variety of functions, including absorption, secretion, cellula ...
.
The stiff projecting portion of coenenchyme that surrounds each
polyp is usually reinforced by modified sclerites and is called the
calyx, a term borrowed from botany. The solenia circulate nutrients throughout the coenenchyme.
Coenosarc
In corals, the coenosarc is the living tissue overlying the stony skeletal material of the coral. It secretes the coenosteum, the layer of skeletal material lying between the corallites (the stony cups in which the polyp (zoology), polyps sit). The ...
is an alternative name.
References
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Cnidarian anatomy