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9 Cards in this Set
- Front
- Back
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What is an open circulatory system? |
Blood isn't always held in blood vessels Instead blood fluid circulates through body cavity - tissues + cells directly bathed in blood |
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How does an insect's muscles help to circulate blood around its body? |
Muscular pumping organ like a heart - long, muscular tube lying under the dorsal surface of insect Blood from body enters heart through its pores - called ostia Heart then pumps blood towards head by peristalsis - at forward end of <3 - blood pours out into cavity |
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Why don't all animals have an open circulatory system? |
Open circ system works for insects bc they're small blood doesn't have to travel far - + don't rely on blood to transport oxy and carbon dioxide They use a separate system for gas exchange Larger organisms rely on blood to transport gases - open circ wouldn't be sufficint bc low pressure + slow flow Not sufficient to supply needs of muscles in large active processes |
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How do closed circulatory systems work? |
Blood stays entirely in vessels Separate fluid called tissue fluid is what bathes cells Enables heart to pump blood at high pressure - so it flows more quickly Thus oxy + nutrients delivered and waste removed more quickly Fish have closed circulatory system heart - arteries - gills - veins - body tissues - veins - heart Must be exchange surfaces at gills and body tissues - to allow material to be exchanged btwn blood and tissue fluid |
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Blood vessels general structure |
Arteries - lumen, endothelium, elastic fibres, smooth muscle, collagen fibres Veins - lumen, endothelium, smooth muscle, collagen fibres Capillaries - lumen, endothelium |
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What is the role of the endothelium in vessels? |
Particularly smooth to reduce friction with slowing blood |
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Describe the structure of the arteries |
Relatively small lumen - maintains high pressure Wall relatively thick + contain collagen = gives it strength to withstand pressure Elastic fibres - allow it to stretch then recoil when heart pumps = recoil maintains high pressure whilst <3 relaxes Smooth muscle in wall - contract + constrict artery - constriction narrows lumen Endothelium - folded + can unfold when artery stretches |
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Describe the structure of the veins |
Lumen is relatively large to ease flow of blood Walls have thinner layers of collagen, smooth muscle and elastic tissues - don't need to stretch + recoil & not actively constricted Main feat. = contain valves to help blood flow back to <3 - + prevent back flow Veins can be flattened by action of skeletal muscle |
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Describe the structure of capillaries |
V thin walls - allow exchange of materials btwn blood + cells of tissues via tissue fluid Wall = single layer of flattened endothelial cells -reducing diffusion distance for materials Narrow lumen - ensures RBCs = squeeazed as passed along capillaries - helps give up their oxygen bc pressed close to walls reducing diffusion path |
