OCR AS Biology Module 2 Circulatory systems/Blood Vessels

Revision cards covering pages 60-61 in OCR Biology textbook. Should hopefully be equally as useful for AQA and Edexcel students. Please, enjoy. :)

  • Created by: JessicaB
  • Created on: 17-11-11 20:31

Open Circulatory Systems



  • All insects have an open circulatory system
  • Blood is not always carried in blood vessels
  • Blood fluid circulates through the body cavity, so tissues are bathed directly in blood.
  • In some animals, the action of body muscles helps to circulate blood
  • In many insects, there is a tubular heart, blood from the body enters the heart through pores called ostia
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Closed Circulatory Systems


  • In larger animals, the blood stay entirely in blood vessels
  • Enables the heart to pump blood at higher pressure
  • Therefore nuitrients are delivered quicker
  • Fish closed circulation:

Heart->Arteries->Gills->Veins->Body Tissues->Veins->Heart

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  • Carries blood away from heart
  • Lumen is relatively small to maintain high pressure
  • Thick wall containing collagen to give it strength
  • Elastic tissue which helps it to stretch and recoil
  • Smooth muscle that can contract and constrict to limit blood flow to certain organs
  • Endothelium is folded and can unfold when artery stretches
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  • Carry blood to the heart
  • Large lumen to ease flow of blood
  • Thinner layers of collagen, smooth muscle and elastic tissue
  • Do not need to stretch and recoil
  • Contain valves to help blood flow back up to the heart.
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Helpful Diagram


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  • Allow exchange of materals between bloodc and cells of tissues
  • Very thin walls to reduce diffusion distance
  • Narow lumen which makes sure the red blood cells are squeezed whilst passing through capillaries. Helps them to givbe up oxygen as pressed close to capillary wall.
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