Practice question

Water vascular system is a unique coelomic derivative exclusive to echinoderms, functioning independently from blood vasculature. Seawater enters via madreporite, passes through stone canal to circumoral ring canal, then to five radial canals branching into lateral canals ending in ampullae and tube feet podia. Coordinated contraction of ampullae hydraulically extends podia for creeping locomotion, firm attachment to rocks, prying bivalve prey and particle gathering in crinoids. Podial epithelium also mediates gas exchange and waste diffusion. Its multifunctional role in locomotion, feeding and respiration underpins echinoderm ecology and distinguishes Ambulacraria.