AQA GCSE Biology Unit B3 Chapter 2.1/2.2 (Circulation)

Bits about circulation from the further biology work

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  • Created by: Lara
  • Created on: 20-05-10 13:49

Double CIrculation

Circulation of the blood is called a "double circulation", this is because blood is pumped from the heart to the rest of the body and back then to the lungs and back.

GS_heart2.gif ( of a simplified diagram but it's fine.

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Arteries carry blood away from the heart.

  • The blood flows in high pressure waves
  • They have thick walls to withstand the high pressure and also because...
  • They have a thick layer of muscle and elastic fibres
  • Lumen are narrow (comparatively)


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Veins carry blood to the heart

  • The blood flows slowly and under low pressure
  • The walls are slightly elastic - no recoil though
  • They have relatively thin walls
  • They often have valves
  • They have wide lumen (comparatively)

( picture, yeah?

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Capillaries connect the arteries to the veins

  • They are tiny vessels with narrow lumen
  • Their walls are a single cell layer thick
  • No elasticity at all
  • Very narrow lumen (red blood cells pass in single file)
  • Blood flows very slowly; glucose and oxygen are delivered to cells (by diffusion)


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The heart


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In one heart beat...


  • Deoxygenated blood enters the right atrium via the vena cava
  • The right atrium contracts and blood passes through the atrioventricular valve into the right ventricle
  • The right ventricle contracts and blood passes out into the pulmonary artery.
  • Blood flows to lungs to get oxygen


  • Oxygenated blood enters the left atrium through the pulmonary vein
  • Left atrium contracts and the blood passes through the atrioventricular valve into the left ventricle
  • The left ventricle contracts and the blood passes out to the body through the aorta, becoming deoxygenated.
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Transport in the blood

Key points

  • Your blood is the main transport medium of your body
  • Your blood plasma transports dissolved food molecules, carbon dioxide and uea
  • Your red blood cells are biconcave discs which have no nucleus and are pack with the red pigment haemoglobin
  • Red blood cells are adapted to transport oxygen from your lungs to the organs of your body
  • Oxygen is carried by haemoglobin which becomes oxyhaemoglobin in a reversible reaction
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do we have to be able to label the heart in this much detail ? aqa exam

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