Describe the structures and functions associated with the water-vascular system echinoderms. Solution Echinodermata represents the phylum of animals in which spiny-skinned organisms are included. All the organisms of this phylum are aquatic in nature and follow either sedentary or mobile life- style. They have penta-radial symmetry in morphology and normally contain tube feets. The peculiar system in these organisms is the presence of a water-vascular canal. The features of these water vascular canals are enlisted as below: Various structures associated with water vascular system are discussed as below: Thus, the above given explanations decipher that the water vascular system of echinoderms is complex and has high physiological value. Madreporite: The madreporite represents the central tube along with which all the other tubules are associated. These water canals open directly on the surface of the organism and generate a water pore through which water can move to and fro. Stone canal: The stone canal is a tender tube associated with the madreporite. It has two openings, one of which opens towards the oral cavity and other towards the axial sinus. It runs longitudinally across the breadth of the organism\'s body. It is normally curved shaped but can be \"S\' shaped in some organisms. Axial sinus: The axial sinus and organ represent some accumulated connective tissues and are of germinal in nature. These axial sinuses directly communicate with the stone canal on their posterior end. Ring canal: The ring canal represents one of the most important organs of the echinoderm. It is a ring shaped structure located near the madreporite on the centre and have extensions of tubules which help in circulation of water and fluid. Since echinoderms have pentaradial symmetry, the ring canal often gives riset to atleast 5 extensions. Lateral vessels and the tube-feet: These are the organs of locomotion present just below the madreporite and lateral pentameric extensions of ring canal. Internally, the tube feet and lateral vessel communicate with the skeleton of water-vascular system..

1. Describe the structures and functions associated with the water-vascular system echinoderms.
Solution
Echinodermata represents the phylum of animals in which spiny-skinned organisms are included.
All the organisms of this phylum are aquatic in nature and follow either sedentary or mobile life-
style. They have penta-radial symmetry in morphology and normally contain tube feets. The
peculiar system in these organisms is the presence of a water-vascular canal. The features of
these water vascular canals are enlisted as below:
Various structures associated with water vascular system are discussed as below:
Thus, the above given explanations decipher that the water vascular system of echinoderms is
complex and has high physiological value.
Madreporite: The madreporite represents the central tube along with which all the other tubules
are associated. These water canals open directly on the surface of the organism and generate a
water pore through which water can move to and fro.
Stone canal: The stone canal is a tender tube associated with the madreporite. It has two
openings, one of which opens towards the oral cavity and other towards the axial sinus. It runs
longitudinally across the breadth of the organism's body. It is normally curved shaped but can be
"S' shaped in some organisms.
Axial sinus: The axial sinus and organ represent some accumulated connective tissues and are of
germinal in nature. These axial sinuses directly communicate with the stone canal on their
posterior end.
Ring canal: The ring canal represents one of the most important organs of the echinoderm. It is a
ring shaped structure located near the madreporite on the centre and have extensions of tubules
which help in circulation of water and fluid. Since echinoderms have pentaradial symmetry, the
ring canal often gives riset to atleast 5 extensions.
Lateral vessels and the tube-feet: These are the organs of locomotion present just below the
madreporite and lateral pentameric extensions of ring canal. Internally, the tube feet and lateral
vessel communicate with the skeleton of water-vascular system.