Explain the differences between open and closed circulatory systems

Open and closed circulatory system are the two types of blood vascular system. In the open circulatory system the fluid is pumped through open-ended vessels & flows out among the cells. According to this, there is no distinction between blood and interstital fluid.
In the closed circulatory system the blood is confined to vessels, which keep it distinct from the interstital fluid.

Organism, organ system, organs, tissue, cells