Water Vascular System of Sea Star

Water Vascular System of Sea Star

• The water vascular system is a modified part of the coelom.
• It's a system of sea water-filled canals with specific corpuscles.
• It's also called the ambulacral system.
• Functions include locomotion, capturing food, and respiration.

Essential Parts of the Water Vascular System

• Madreporite: A rounded calcareous plate on the aboral surface of the central disc. It has radiating grooves and pores. The pores lead into canals that collect water.
• Stone canal: Connects the madreporite to the ring canal. It's lined with tall flagellated cells.
• Ring canal: A ring located inside the peristomial ring of ossicles, above the hypo-neural ring sinus.
• Radial canal: Extend from the ring canal into each arm.
• Tiedemann's bodies: Small yellowish, irregular or rounded bodies, inter-radially, from the ring canal, possibly lymphatic glands.
• Polian vesicles: Pear-shaped bladders connected to the ring canal, regulating pressure and producing amoeboid cells.
• Lateral canals: Short, narrow branches extending from the radial canals, connected to tube feet.
• Tube feet: Hollow, elastic, thin-walled structures with an ampulla, a podium, and a sucker. They are the primary means of locomotion, respiration, sensing, and capturing food.

Detailed Descriptions of Key Components

• Madreporite (i): Its surface has wavy grooves or furrows containing minute pores, leading to canals uniting to form collecting canals. These canals open to an ampulla.
• Stone canal (ii): The ampulla opens into an S-shaped stone canal, descending to the ring canal, and lined with tall flagellated cells. In adult Asterias, it contains ridges with spirally rolled lamellae.
• Ring canal (iii): Located inner side of the peristomial ring and above the hypo-neural ring sinus, its shape is pentagonal
• Tiedemann's Bodies (iv): Inter-radially located small, yellowish glandular bodies, attached to the peristomial ring ossicles; they are hypothesized to create amoeboid cells for the system.

Additional Components

• Polian vesicles (v): Situated within the inter-radial area of the ring canal, little pear-like, thin-walled, and contractile bladders
• Radial canals (vi): Extend throughout each arm from the ring canal, terminating at the terminal tentacle, running immediately to the oral side of the ambulacral muscles.
• Lateral canals (vii): short branches extending from the radial canals, attached to tube feet. They possess a valve preventing backward water flow. tube feet connected to lateral canals.

Tube Feet (viii)

• Tube feet are found in four rows in each ambulacral groove within each arm.
• They're thin-walled, closed-cylinder structures with an upper sac-like ampulla, a middle podium, and a lower disc-like sucker.
• Their purpose is primarily locomotion, respiration, sensing, and food capture.

Locomotion on a Horizontal Surface

• An Asterias moves by contracting the ampullae, forcing water into the podia, extending the tube feet.
• Podia attach to the substrate and the muscles contract, moving the animal. This process is repeated for further movement.

Explore the fascinating water vascular system of sea stars, also known as the ambulacral system. This quiz covers its essential parts, such as the madreporite, stone canal, and radial canals, along with their functions in locomotion and respiration. Test your knowledge on how these components work together for the sea star's survival.