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4. Circulation I & II

4. Circulation I & II - Biology107Fall07...

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Biology 107 – Fall ’07 Circulation I & II 1 Circulation: Reading:  Chapter 42 INTRODUCTION – CIRCULATION IN ANIMALS Transport systems functionally connect organs of exchange with body cells o Diffusion is too slow a process to transport chemicals throughout body of large animal o Therefore – need a  bulk transport  system to accomplish transport of materials to within “diffusing  distance”.  o Example of bulk transport system:  our own (human) closed circulation Bulk fluid movement is powered by heart Blood moves through vessels to tissues Exchange (diffusion) between blood and interstitial fluid occurs across capillaries  Categories of internal transport systems: o Gastrovascular Cavities :  e.g.,  Aurelia  (moon jelly); Hydra – Fig. 42.2; 41.13; flatworms Single opening Fluid in cavity is continuous with water outside Body walls only two cells thick Does both digestion and distribution o Open Circulatory System :  e.g., grasshopper (fig. 42.3a) No distinction between blood and interstitial fluid –  hemolymph  is therefore the “fluid” for  bulk transport Heart(s) pump hemolymph through vessels to  sinuses  which surround organs. Hemolymph returns to heart(s) via  ostia Examples:  Insects; Crustaceans (crayfish, lobsters) and many Mollusks Hemolymph bathes tissues/organs in sinuses No capillaries Exchange occurs in sinuses o Closed Circulatory System: Blood confined to vessels, and is distinct from interstitial fluid.  Allow gill- or lung- breathing. Simple closed circulatory system – earthworm (fig. 42.3) Heart  pumps blood around closed circuit. Ventricle(s)  pump blood into  arteries , which carry blood away  from heart Veins  return blood to  heart (specifically, to  atria )
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Biology 107 – Fall ’07 Circulation I & II 2 Exchange  occurs across  capillaries Examples : Earthworms, squid, octopus, and vertebrates Both open and closed circulatory systems have… 1. a circulatory fluid  Open system = hemolymph Closed system = blood 2. Set of vessels 3. Muscular pump (heart)
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4. Circulation I & II - Biology107Fall07...

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