Demospongiae

-most common class of Porifera

-spongin and silicon dioxide spicules (some have external layer of aragonite)

Hexactinellida

-glass sponges

-six-sided silicon dioxide spicules

Calcarea

totipotent

cells which can be differentiated or redifferentiated at any time to perform any of various cell functions

sclerocytes

sponge cells which produce spicules

spongin

intercellular matrix composed of collagen layers for structural support

choanocyte

cells lining the inside of the sponge composed of the cell body, a "collar" of microvilli which filter food particles, and a beating flagellum which draws water through the sponge wall

porocyte

bead-shaped cells that line the outside of a sponge with a hole called an ostium, allowing water to flow through it

spongocoel

the main cavity of a sponge

osculum

the opening of the sponge, through which filtered water is pushed out

amoebocytes

mobile sponge cells which can perform any function as needed, like sponge minute men

pinacocyte

sponge cells that can expand or contract to change the form of the sponge body