Open & Closed Circulatory Systems

Circulatory system is responsible for movement of nutrients, gases and wastes within blood vessels.

Open and Closed Circulatory Systems

Circulatory system is not found in Porifera, Cnidaria, Platyhelminthes, Nematodes and Echinoderms. An open circulatory system is found in arthropods, gastropods, bivalves and protochordates. In open circulatory system blood (called hemolymph) flows in vessels as well as open in body cavities. Such circulatory system has low blood pressure.

In annelids, Cephalopods and Vertebrates, closed circulatory system in found in which blood circulates only inside blood vessels. Due to this, the blood pressure is high in these organisms and thus blood can travel greater distances to the organs and tissues. Further, higher circulatory speed also increases the capacity to distribute large supplies of oxygen.