3 circulation and respiration 2010

3 circulation and respiration 2010 - Biology 5B Circulation...

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Unformatted text preview: Biology 5B Circulation and Respiration 0.15 mm O 2 CO 2 All organisms must exchange materials with the environment. The exchange of gases used in cellular respiration (O 2 and CO 2 ) is one of the most important processes in an animals physiology Most gases move easily through membranes by diffusion. Although diffusion requires no energy it is a random process and it is relatively slow. Therefore, duffusion is fine for single celled and very small animals Larger animals must build distributive systems for the transport of gas and other materials Distributive systems take advantage of convection through circulating blood to carry materials from one place to another in the body quickly and efficiently CONCEPT: 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 Diffusion is only viable if it is fast enough to support cellular and organismal processes In almost all animals that distance is less 10 mm and effective over one or two cell layers Gastrovascular Cavities Simple animals, such as cnidarians, have a body wall that is only two cells thick. It encloses a gastrovascular cavity here diffusion might be possible This cavity functions in both digestion and distribution of substances throughout the body Cnidarians, such as jellies, have elaborate gastrovascular cavities Flatworms have a gastrovascular cavity and a large surface area to volume ratio Circular canal Radial canal Mouth (a) The moon jelly Aurelia , a cnidarian The planarian Dugesia , a flatworm (b) Mouth Pharynx 2 mm 5 cm 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, the general body fluid is called hemolymph Heart Hemolymph in sinuses surrounding organs (a) An open circulatory system Tubular heart Pores In a closed circulatory system , blood is confined to vessels and is distinct from the interstitial fluid Closed systems are more efficient at transporting circulatory fluids to tissues and cells Heart Interstitial fluid Small branch vessels In each organ Blood Dorsal vessel (main heart) Auxiliary hearts Ventral vessels (b) A closed circulatory system Organization of Vertebrate Circulatory Systems Humans and other vertebrates have a closed circulatory system, often called the cardiovascular system The three main types of blood vessels are arteries, veins, and capillaries Arteries branch into arterioles and carry blood to capillaries Networks of capillaries called capillary beds...
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This note was uploaded on 07/31/2010 for the course BIOL005C BIOL005C taught by Professor Walton during the Spring '08 term at UC Riverside.

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3 circulation and respiration 2010 - Biology 5B Circulation...

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