They have no heart brain nor eyes but some brittle

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They have no heart, brain, nor eyes, but some brittle stars seem to have light sensitive parts on their arms. Their mouth is situated on the underside and their anus on top. Echinoderms have tentacle-like structures called tube feet with suction pads situated at their extremities. These tube feet are hydraulically controlled by a remarkable vascular system. This system supplies water through canals of small muscular tubes to the tube feet (ambulacral feet). As the tube feet press against a moving object, water is withdrawn from them, resulting in a suction effect. When water returns to the canals, suction is 1
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released. The resulting locomotion is generally very slow. 2. List the structures that are visible on the oral surface of the starfish. Structures visible on the oral surface are tube feet, ambulactral grooves, pyloric and cardiac stomach, pyloric ducts, pyloric ceca, gonad, stone canal, ring canal, radial canal and ambulacral ridge. 3. List the structures that are visible on the aboral surface of the starfish. Structures visible on the aboral surface are madreporite plate, dermal spines, dermal branchiae, and pedicullarie. 4. List, in order, all the parts of the water vascular system of the starfish and explain the purpose of this series of water-filled tubes and chambers. 1. madreporite, 2. stone canal, 3. ring canal, 4. Polian vesicles, 5. Tiedmann’s bodies, 6. Radial canals, 7. Lateral or Podial canals, 8. Tube feet (Podia) and Ampulla. The water vascular system controls the tube feet hydraulically through a complex of fluid filled canals and reservoirs. The madreporite is located next to the central disk and takes in water. The water continues to the stone canal to the ring canal and into the radial canals, located in each arm. The radial canals carry water to the ampullae and provide
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  • Fall '15
  • Onefator
  • Digestive System, Phylum Echinodermata

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