The radial canals run through notches in the calcareous plates surrounding the mouth and then run along the ambulacral areas along the length of the body.
22.
Its main parts are the madreporite, the stone canal, the ring canal, the radial canals, the lateral canals, and the tube feet.
23.
In many species, this is further elaborated by a system of radial canals, with or without an additional ring canal towards the edge of the dome.
24.
The ampullae branching off from either side of the radial canals give rise to ten rows of tube feet, which penetrate through holes in the test to the outside.
25.
The Apodida, which have no tube feet, also have no radial canals, with the canals to the tentacles branching off directly from the ring canal . 991 992
26.
A central haemal ring surrounds the pharynx next to the ring canal of the water vascular system, and sends off additional vessels along the radial canals beneath the ambulacral areas.
27.
In sea stars these are always staggered, so that an ampulla on the left follows one on the right, and so on down the length of the radial canal.
28.
The central ring canal, in addition to connecting the radial canals to each other and to the stone canal, also has a number of other specialised structures on the inner surface.
29.
Radial canals in the endosiphuncular canal system are typically arched, curving forward and backward from near the septal foramina ( openings ) to connect with the parispatium on either side of the middle of each segments.
30.
While a starfish lacks a centralized brain, it has a complex nervous system with a nerve ring around the mouth and a radial nerve running along the ambulacral region of each arm parallel to the radial canal.
