Brittle stars have five long and narrow flexible arms attached to a round disk-like body. Inside the disk are all the organs.
The flexible arms are used for locomotion. The arms have muscles that help them to move and bend. The spines along the side of the arms provide grip.
The tube feet help brittle stars to feed. They move small items of food towards the mouth. They often eat decaying material or small microscopic food items floating in the water. The digestive system in the small disk is only five dead end sacks. The mouth must also function as an anus.