Q. What is an open circulatory system?
Open circulatory system is the one in which blood doesn't circulate only inside blood vessels but it also falls in cavities that irrigate tissues. In the open circulatory system the blood pressure is low and generally the blood called as hemolymph has low cellularity. Arthropods, protochordates and molluscs (the cephalopods are exception) have open circulatory system.