GENERAL HISTOLOGY

Detailed explanation-1: -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.

Detailed explanation-2: -The water vascular system consists of fluid-filled canals that extend to different parts of the body. Water enters the water vascular canal through the madreporite.

Detailed explanation-3: -The components of the water vascular system of echinoderms. Water enters the system through the madreporite, flows through the stone canal, and enters the ring canal. A number of bulbous structures, called polian vesicles, that branch off of the ring canal serve as reservoirs to maintain extra water stores.

Detailed explanation-4: -The water vascular system is an important character in the echinoderms as the organisms reside in the aquatic environment. Water enters the vascular system through a structure known as madreporite. This is the structure through which echinoderms take in seawater and also expels the water outside the system.

Detailed explanation-5: -n. A structure in echinoderms through which water can flow in either direction between the water vascular system and the surrounding sea. Also known as a madreporite.