The Crinoid Water Vascular System

Echinoderms are characterized by a unique coelomic water vascular system. This is a hydraulically controlled system consisting of a circumoral ring around the esophogus with connecting radial canals each leading to an ambulacrum. The radial canals in crinoids run along each arm into an ambulcral groove and tube feet. The ambulacral groove with its many cilia and hydraulically driven tube feet manipulate captured food down the ambulacral grooves along the arms down to the mouth, situated at the tegmen which is positioned at the base of the arms. Echinoderm water vascular systems are either open or closed, crinoids all have an open water vascular system. If the radial canals run down the ambulacral grooves and are not covered by plates then the system is considered "open", if the radial canals are primarily internal and externalized through pores, the system is "closed".