BIOL 1082 Lecture Notes - Lecture 18: Viscosity, Partial Pressure, Countercurrent Exchange
Document Summary
Circulation and gas exchange i (reading: concepts: 42. 1 & 42. 5 in textbook: list animals that have open and closed circulatory systems, as well as some that have none, comparing and contrasting the structure and function of each approach. In an open circulatory system, the circulatory fluid, called hemolymph, is also the interstitial fluid that bathes body cells. Heart contraction pumps the hemolymph through the circulatory vessels into interconnected sinuses, spaces surrounding organs. Within the sinuses, chemical exchange occurs between the hemolymph and body cells. Relaxation of the heart draws hemolymph back in through pores, which are equipped with valves that close when the heart contracts. Body movements periodically squeeze the sinuses, helping circulate the hemolymph. Larger crustaceans include a more extensive system of vessels as well as an accessory pump. Animals: arthropods, grasshoppers, molluscs, clams, lobsters and crabs. In a closed circulatory system, a circulatory fluid called blood is confined to vessels and is distinct from the interstitial fluid.
