Starfish

Starfish move using a water vascular system. Water comes into the system via the madreporite. It is then circulated from the stone canal to the ring canal and into the radial canals. The madreporite is a rounded plate on the aboral surface of the central disc in inter-radial position. Its surface bears a number of narrow, straight or wavy grooves or furrows. Each furrow contains many minute pores at its bottom. Each pore leads into a very short, fine, tubular pore-canal. The pore-canals unite to form the collecting canals. Which open into an ampulla beneath the madreporite. The ampulla opens into a "S" shaped stone canal. The stone canal extends downwards (orally) and opens into a ring canal, around the mouth. The radial canals carry water to the reservoir (ampulla) portion of tube feet. Each tube foot consists of an internal ampulla and an external podium, or foot. When the ampulla is squeezed, it forces water into the podium, which expands to contact the substrate, a layer that underlies the sea star ex: rocks. In some circumstances the tube feet …show more content…
Suspension-feeding starfish use their tube feet to pass food to the mouth. The cardiac stomach is connected to a pyloric stomach (located above it), which in turn is connected to both the anus. The digestive glands and the cardiac stomach produce digestive enzymes. Digested material is absorbed through the digestive glands for transport to the rest of the body. Since the digestive glands extend the length of each arm, the need for an advanced circulatory system is reduced. The water vascular system uses cilia and the constant contraction of ampulla to extend and retract the tube feet, also helps keep things moving. Oxygen enters mainly by diffusion into the tube feet and thus into the water vascular system which allows for the digestive system to