Echinodermata (Starfish, Urchins, sea cucumbers)
Echinoderms are a phylum of marine animals. The adults are recognizable by their radial symmetry, and include such well-known animals as starfish, sea urchins, and sea cucumbers. Animals of this phylum have less developed circulatory system
Starfish:
Starfish do not have a true circulatory system. An extension of the stomach known as “pyloric cecum” extends throughout each of the arms of the starfish and supplies nutrients to all parts of the body. Thus, starfish do not need a true circulatory system. Starfish also have no true heart or anything that more than merely resembles a circulatory system. Starfish have a well structured system of tubes that works in lieu for the circulatory system.
Sea Cucumber:
A sea cucumber, has a closed circulatory system which is unique in its degree of
development for the phylum Echinodermata. Basically the blood vascular system consists of two major vessels running parallel to the gut: the dorsal vessel pumps colorless blood via the vessels within the walls of the intestine into the ventral vessel. There are two specialized areas of the circulation: (1) At the upper small intestine 120 to 150 muscular single-chambered hearts pump blood from the dorsal vessel into a series of intestinal plates. (2) At the lower region of the small intestine the vasculature is associated with the left respiratory tree. Blood passing from the dorsal pulmonary vessel can take two routes to the gut, it either passes through myriads of minute respiratory shunt vessels entangled with the respiratory tree or it passes through a unique follicle network consisting of tiny channels periodically dilated into chambers filled with iron deposits, necrotic cells and developing coelomocytes.
development for the phylum Echinodermata. Basically the blood vascular system consists of two major vessels running parallel to the gut: the dorsal vessel pumps colorless blood via the vessels within the walls of the intestine into the ventral vessel. There are two specialized areas of the circulation: (1) At the upper small intestine 120 to 150 muscular single-chambered hearts pump blood from the dorsal vessel into a series of intestinal plates. (2) At the lower region of the small intestine the vasculature is associated with the left respiratory tree. Blood passing from the dorsal pulmonary vessel can take two routes to the gut, it either passes through myriads of minute respiratory shunt vessels entangled with the respiratory tree or it passes through a unique follicle network consisting of tiny channels periodically dilated into chambers filled with iron deposits, necrotic cells and developing coelomocytes.