What is meant by open and closed circulatory system
Open circulatory system:- In this system, blood, i.e hemolymph (blood+interstitial fluid) is pumped through heart directly into hemocoel or body cavity where it surrounds the organs. Maintain smaller blood pressure e.g. Grasshopper.
Closed circulatory system:- It comprised of circulatory fluid (blood) enclosed in blood vessels. Blood circulation is through pumping action of the heart pushing blood through closed vessels. Maintain high blood pressure. e.g. all vertebrates and a few invertebrates.