GENERAL HISTOLOGY

Detailed explanation-1: -Water enters through the madreporite and flows through a tube, called the stone canal, that connects to the circular ring canal surrounding the mouth. From there, water can flow into five radial canals that branch off the circular ring.

Detailed explanation-2: -Water enters through the madreporite into the ring canal and from thence into the radial canals to the ampullae and finally into the tube feet. This shows the correct sequence of events. The water vascular system helps in locomotion and suspension feeding in certain classes.

Detailed explanation-3: -In sea stars, water enters the system through a sieve-like structure on the upper surface of the animal, called the madreporite. This overlies a small sac, or ampulla, connected to a duct termed the stone canal, which is, as its name implies, commonly lined with calcareous material.