What is the structure and function of an endo skeleton in echinoderms?

Echinoderms possess a unique endoskeleton composed primarily of calcareous plates or ossicles, which are embedded within their mesodermal tissue. This endoskeleton provides structural support and protection while allowing for flexibility and movement, particularly through the use of tube feet. The ossicles can vary in size and shape, contributing to the diverse forms of echinoderms such as sea stars, sea urchins, and sea cucumbers. Additionally, the endoskeleton plays a role in locomotion and defense against predators.