The water vascular system of echinoderms consists of a network of canals filled with fluid connected to the coelom. It contains structures like the madreporite, stone canal, ring canal, radial canals, and tube feet. The system functions in locomotion, food capture, attachment, and sometimes respiration, excretion, and sensation. It varies in structure across the different echinoderm classes.

1. WATER VASCULAR SYSTEM/AMBULACRAL SYSTEM
IN ECHINODERMS
•System of canals & associated structure filled with
watery fluid containing
•Entire system derived from the coelom (hydrocoel), the
canals are lined by ciliated epithelium.
•Basic components : madreporite, stone canal, ring canal,
radial canal and tube feet
•It is variously modified in the different classes of
echinodermata.

2. Water Vascular System in Asteroidea
•Components
•Madreporite-
Hard, circular, porous, calcareous plate
Found on the aboral surface of the disc inter-radially.
 Surface carries a number of radiating narrow furrows
/grooves.
 Bottom of these grooves are perforated by minute
pores.
Each pore leads into a pore canal.
Pore canals in turn unite to form several collecting
canals which open into a small sac-like ampulla below.
 Ampulla leads into the stone canal.

3. Stone Canal:
•S-shaped canal extending from the madreporite to the
ring canal.
• Wall strengthened calcareous rings
• lumen of the canal is divided by a longitudinal ridge.
•Ring Canal: Ring canal is a wide
• pentagonal canal lying around the oesophagus.
Polian Vesicles: ring canal bears on its outerside five, thin
walled, flask shaped, contractile structures called Polian
vesicles.
•They store sea water
• help to regulate hydrostatic pressure inside the system
by quickly emptying the water.

4. Tiedemann's Bodies/Racemose Glands:
•Small, rounded, yellowish, glandular bodies
•Lymphatic glands involved in the production of corpuscles
found in the water vascular system.
Radial Canals: 5 radial canals arise from the five angles of
the ring canal externally.
•Each radial canal runs into an arm above the ambulacral
groove and terminates in a short tentacle at the tip.
Lateral Canals: In each arm, the radial canal gives out on its
lateral sides two rows of short, narrow, branches called
lateral canals.
•Each lateral canal carries a tube feet at its tip.
• Lateral canals are provided with valves which prevent flow
of water back to the radial canal.
•The valves are placed at the junction of lateral canal and
ampulla.

5. •Tube feet: Elastic,thin walled,hollow closed cylinderlike
structure
•Three distinct region : ampulla,podum adhesive disc
•Ampulla- upper rounded sac like part of the tube foot
•Podium- middle tubular part
•Adhesive disc – terminal cup like part

6. Water Vascular System in Ophiuroidea
•Madreporite : oral in position & usually bears a single pore
canal.
•Stone canal: runs upward to join the ring canal.
•Ring canal : situated in a grove on the aboral side ofthe jaw
apparatus.
•Ring canal gives off polian vesicles in each interradius
except the one which bears the stone canal.
•Polian vesicles are accompanied by long, slender, tubular
appendages of unknown function, known as simroth's
appendages.
• Tiedemann's bodies are absent.
•V-shaped lateral canals originate from the radial canals and
terminate in tube
•Tube feet are poorly developed without ampulla and sucker.

7. •Water Vascular System in Class Echinoidea
•Madreporite - aboral and leads to a ventral sinus through
many pore canals.
•Stone canal descend orally to join the ring canal.
•Ring canal lies just above the masticatory apparatus
(aristotle's lantern).
•Five polian vesicles and five tiedemann's bodies present.
•Radial canals rise up to run along the under side of
ambulacral areas of the test.
•Radial canal gives off lateral canals alternatively on both
sides.
•Each tube foot consists of ampulla, podium and sucker.

8. Water vascular system in holothuroidea
•Madreporite lies in the coelom and does not communicate with the
exterior.
•Stone canal usually divided into a bunch of smaller canals,
extending between madreporite and ring canal.
•Ring canal encircles the pharynx.
•Number of polian vesicle –one
•Tiedemann's bodies absent.
•Five radial canals arise from the ring canal and run anterior wards.
•Tube feet on the ventral side are provided with suckers , used for
locomotion, while those on the dorsal side are without suckers and
probably sensory in function.
•In apoda, tube feet are absent, water vascular system is limited to
the water ring, polian vesicle and buccal podia (tentacles).

9. Water Vascular System in Crinoidea
•Madreporite is absent.
•Ring canal encircling the mouth gives off stone canals hanging
freely in the coelom.
• 5 radial canals originate from the ring canal.
•Each radial canal after entering an arm bifurcates and divides to
supply all of the branches and pinnules.
•Lateral canals originating from the radial canals supply the tube
feet.
•Tube feet lack ampullae and suckers and are covered with cilia
•Tegmen is perforated ciliated, funnel shaped water pores
(ciliated funnels) that open into the coelom internally.
•Tiedemann's bodies and polian vesicles are absent.

10. Functions of Water Vascular System
•Locomotion: musculature provides a hydraulic pressure
mechanism responsible for movement. The wall of ampulla is
formed mainly of circular muscles while that of podium comprises
longitudinal muscles.
•filled with a fluid similar to sea water and any slight loss of fluid in
the system is compensated by sea water intake through the
madreporite.
•beating of the cilia of the ambulacral system facilitates the entry of
water into the system.
•This fluid moves through stone canal, ring canal, radial canals,
lateral canals and finally reaches the ampullae of the tube feet.
•During movement the tube feet perform a sort of stepping action

11. •Food Capture: While feeding, the tube feet are used to
hold the prey and also to open the shells of molluscs.
•Attachment: The suckers of the tube feet help the animal
to remain anchored to rocks and other hard substrata.
•Respiration, Excretion and Sensation: In many
echinoderms, the tube feet are not locomotory in function.
Instead, they become modified to serve as respiratory,
sensory and excretory structures (eg. sea cucumber, sea
lily, etc.).