Table of contents |
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Locomotion in Echinoderms: The Water-Vascular System |
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Structure of the Water-Vascular System |
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Accessory Structures |
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Locomotion and Functions of Tube Feet |
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Polian Vesicles: These pear-shaped appendages are attached to the ring canal in inter-radial positions. They possess long necks and thin walls, and are believed to be involved in regulating fluid pressure within the system and in producing amoeboid cells.
Tiedemann's Bodies: This pair of small glandular structures is found near the neck region of the Polian vesicles, with two in each inter-radius (except where the madreporite is present). Their exact function is still under investigation, but they are considered to be lymphatic glands.
Overall, the water-vascular system, with its fluid-filled tube feet, plays a vital role in the locomotion of echinoderms. The hydraulic pressure generated by this system enables the extension and adhesion of tube feet, allowing these unique marine animals to move, albeit at a slow pace compared to other animals.
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