Lecture14-1.circulation_and_gas_exchange

Lecture14-1.circulation_and_gas_exchange - Circulation and...

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Circulation and Gas Exchange
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Trading with the Environment Every organism must exchange materials with its environment Exchanges ultimately occur at the cellular level
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In many animals, these exchanges occur directly with the environment sponges, cnidarians, flatworms
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Gastrovascular Cavities Simple animals, such as cnidarians, have a body wall only two cells thick that encloses a gastrovascular cavity This cavity functions in both digestion and distribution of substances throughout the body
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For most cells making up multicellular organisms, direct exchange with the environment is not possible
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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) Elevates hydrostatic pressure (blood pressure) to force fluid movement
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Open Circulatory System In insects, other arthropods, and most mollusks blood bathes the organs directly in an open circulatory system
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Open Circulatory System There is no distinction between blood and interstitial fluid, and this general body fluid is more correctly called hemolymph Exchange between the hemolymph and the body cells occurs in an interconnected system of sinuses
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Closed Circulatory System 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
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Closed Circulatory System Found in annelids, cephalopods, and all vertebrates
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Vertebrate Circulatory Systems Humans and other vertebrates have a closed circulatory system, often called the cardiovascular system Blood flows in a closed cardiovascular system, consisting of blood vessels and a two- to four- chambered heart
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Arteries carry blood to capillaries, the sites of chemical exchange between the blood and interstitial fluid Veins return blood from capillaries to the heart
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The chambers that receive blood entering the heart are called atria The chambers that pump blood out of the heart are the ventricles
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Single Circulation The blood passes through the heart once in each complete circuit Bony fishes, rays, and sharks the heart consists of two chambers Atrium and ventricle
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Gill circulation Blood pumped from the ventricle travels to the gills, where it picks up O 2 and disposes of CO 2 Systemic circulation Oxygen-rich blood is carried to all other parts of the body and returns in veins to the atrium
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Double Circulation Amphibians , reptiles, and mammals have two distinct circuits One pump, the right side of the heart delivers oxygen-poor blood to the places of gas exchange Pulmonary circuit or pulmocutaneous circuit
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Oxygen-enriched blood enters the other pump, the left side of the heart Contractions of this pump deliver oxygen and
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This note was uploaded on 11/02/2010 for the course CHEM 51LA 56555 taught by Professor Guan during the Spring '10 term at UC Irvine.

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Lecture14-1.circulation_and_gas_exchange - Circulation and...

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