Fig. 3.

Starfish anatomy. a Schematic vertical section of the central disc and the proximal region of an arm. b Schematic transverse section of an arm. c Schematic transverse section of a radial nerve cord. Abbreviations: a, anus; am, apical muscle; amp, ampulla; conr, circumoral nerve ring; cs, cardiac stomach; cut, cuticle; ec, ectoneural region; g, gonad; gcc, general coelomic cavity; hy, hyponeural region; m, mouth; md, madreporite; mn, marginal nerve; o, ossicle; p, papula; pc, pyloric caecum; pd., pyloric duct; ped, pedicellaria; pm, peristomial membrane; ps, pyloric stomach; rc, rectal caecum; rca, ring canal; rn, radial nerve; rw, radial water vascular canal; sp., spine; sc, stone canal; tb, Tiedemann’s body; tf, tube foot