: Zooids secrete a protective chamber called a zooecium, which can be gelatinous, chitinous (like insect shells), or calcified (like coral).

Bryozoan colonies are made up of individual units called . These zooids are typically less than 1 millimeter long and cooperate to ensure the colony's survival.

: They possess a U-shaped digestive tract with both a mouth and an anus. Because the anus is located outside the tentacle crown, they are also known as Ectoprocta ("outside anus").