Ch. 42 Circulation and gas Exchange Open Circulatory System Insects (other arthropods) and molluscs No distinction between blood and interstitial fluid. Hemolymph – body fluid Body movements squeeze sinuses which moves hemolymph Closed Circulatory System Earthworms, squids, all vertebrates Blood in vessels separate from interstitial fluid Heart pumps blood into vessels. Blood Vessels Arteries – Blood Away from the heart Veins – Blood to the heart Capillaries – tiny vessels. Blood supply can vary depending on the site of capillaries. Ex. Digestive system capillaries will fill with blood after a meal. Components of Blood Plasma, RBC (transport O2), WBC (immune) and platelets. Blood Clots caused by fibrin protein. Self sealing material after a cut or scrape.