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Chapter 34 Biology

Chapter 34 Biology - Chapter 34 Lesson One The Nature of...

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Chapter 34 Lesson One: The Nature of Blood Circulation Circulatory System: moves substances into and out of cellular neighborhoods. Blood: transport medium, typically flows inside tubular vessels under pressure generated by the a heart Heart: muscular pump Interstitial fluid: fluid in tissue spaces between cells, which exchange substances with cells. Body’s internal environment components are. . 1) blood 2) interstitial fluid Structurally two main kinds of circulator systems 1) Open circulatory system Anthropods and most mollusks Blood moves through hearts, large vessels, also mixes with interstititial fluid 2) Closed circulatory system Annelids and vertebrates Blood remains inside a heart or blood vessel at all times (does not mix) Total volume of blood moves continually away from the heart through vessels then back to the heart Moves fastest in large, few, vessels Moves slowest in blood capillaries Blood capillaries: the vessels with the smallest diameter The slow speed of the capillaries gives blood time to exchange, by diffusion , substances with the interstitial fluid. The slow speed is due to the small diameter and their large amount (billions) a narrow river (few large vessels) were delivering water (blood) into a wide lake (the many capillaries). Figure 34:2 Grasshopper has an open system which has a heart that pumps blood through a large vessel, a type of aorta . From there blood moves into tissue spaces , mixes with interstitial fluid then renters the heart at openings in the heart wall . Earthworm has an closed system which confines blood inside pairs of muscular hearts near the head end and inside many blood vessels. Evolution of Circulation in vertebrates All vertebrate s have a closed circulatory system fishes, amphibians, birds, and mammals differ in their pumps and plumbing The differences evolved after some vertebrates left the water for land Time line of evolution Earliest vertebrates= had gills
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Gills (respiratory structures) have a thin, moist surface, which oxygen and carbon dioxide diffuse across. Internally moistened sacs aka lungs evolved to support the move to land Fish. . Blood flows in one circuit o Blood flow driven by contractile force of a two-chambered heart o Blood flow: heart, capillary bed of each gill, large vessel, capillary beds in body tissues/organs, heart Due to the lack in blood (fluid) pressure when it leaves the gill capillaries, the blood moves slowly through the single circuit (back to the heart) Amphibians Heart divided into three chambers Has two atria emptying into one ventricle Blood flow in one circuit, then second circuit (partially separated) o Oxygenated blood flows from the lungs to the heart in one circuit o Has a forceful contraction that pumps it through the rest of the body in a second circuit Oxygenated blood and oxygenated poor blood mixed a bit in the ventricle In birds and mammals Heart has a fully separate
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Chapter 34 Biology - Chapter 34 Lesson One The Nature of...

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