TAILIEUCHUNG - Lecture Biology: Chapter 42 - Niel Campbell, Jane Reece

Chapter 42 - Circulation and gas exchange. After studying this chapter you will be able to: Compare and contrast open and closed circulatory systems; compare and contrast the circulatory systems of fish, amphibians, reptiles, and mammals or birds; distinguish between pulmonary and systemic circuits and explain the function of each; trace the path of a red blood cell through the human heart, pulmonary circuit, and systemic circuit;. | Chapter 42 Circulation and Gas Exchange Overview: Trading Places Every organism must exchange materials with its environment. Exchanges ultimately occur at the cellular level. In unicellular organisms, these exchanges occur directly with the environment. For most cells making up multicellular organisms, direct exchange with the environment is not possible. Gills are an example of a specialized exchange system in animals. Internal transport and gas exchange are functionally related in most animals. How does a feathery fringe help this animal survive? Figure How does a feathery fringe help this animal survive? Circulatory systems link exchange surfaces with cells throughout the body In small and/or thin animals, cells can exchange materials directly with the surrounding medium. In most animals, transport systems connect the organs of exchange with the body cells. Most complex animals have internal transport systems that circulate fluid. Gastrovascular Cavities Simple animals, such as cnidarians, have a body wall that is only two cells thick and that encloses a gastrovascular cavity. This cavity functions in both digestion and distribution of substances throughout the body. Some cnidarians, such as jellies, have elaborate gastrovascular cavities. Flatworms have a gastrovascular cavity and a large surface area to volume ratio. Internal transport in gastrovascular cavities Circular canal Radial canal Mouth (a) The moon jelly Aurelia, a cnidarian The planarian Dugesia, a flatworm (b) Mouth Pharynx 2 mm 5 cm Figure Internal transport in gastrovascular cavities Open and Closed Circulatory Systems More complex animals have either open or closed circulatory systems. Both systems have three basic components: A circulatory fluid = blood or hemolymph. A set of tubes = blood vessels. A muscular pump = the heart. In insects, other arthropods, and most molluscs, blood bathes the organs directly in an open circulatory system. In an open circulatory system, there is .

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