English: Above is a diagram of an open circulatory system. An open circulatory system is made up of a heart, vessels, and hemolymph. This diagram shows how the hemolymph, fluid present in most invertebrates that is equivalent to blood, is circulated throughout the body of a grasshopper. The hymolymph is first pumped through the heart, into the aorta, dispersed into the head and throughout the hemocoel, then back through the ostium that are located in the heart, where the process is repeated.