B2: The heart and circulatory system

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  • Created by: rachelmu
  • Created on: 29-10-15 16:10

Heart (G-E)

  • The heart lies inside the chest cavity, protected by the rib cage
  • Much of wall of heart made of cardiac muscle
    • This muscle contracts and relaxes to pump blodd
  • Heart has 4 chambers: 2 atria (singular atrium) and 2 ventricles
  • Wall of left ventricle thicker than wall of right ventricle
    • Left ventricle has to pump blood to whole body
    • Right ventricle only pumps blood to lungs so less effort required
  • 4 main blood vessels: pulmonary artery, pulmonary vein, vena cava, aorta
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Heart (D-C)

  • The heart is a double pump
  • Left atrium and ventricle pump oxygenated blood from lungs to rest of body
  • Right atrium and ventricle pump deoxygenated blood to lungs where it is oxygenated

Left atrium -> left ventricle -> aorta -> body capillaries -> right atrium -> right ventricle -> pulmonary artery -> lung capillaries -> pulmonary vein -> left atrium etc

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Heart (B-A*)

  • When the muscular walls of the heart relax, blood fills the chamber
  • When the muscles contract, blood is forced from the chambers
  • The valves control the flow of blood through the heart and arteries leading from the heart
    • This prevents backflow
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The circulatory system (G-E)

  • Network of arteries and veins
  • Heart pumps blood through arteries to body tissues
  • Blood drains from the tissue through the veins back to the heart
  • Capillaries link arteries and veins
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The circulatory system (D-C)

  • Blood in veins flows slower than blood in arteries
    • Blood in veins at lower pressure
  • Large diameter of veins allows blood to flow better
  • Blood flow through veins is helped by contractions of muscles in arms and kegs through which the veins pass
  • Heart pumps blood into arteries at high pressure
    • Blood needs to reach the extremeties of the body
  • Elastic fibres in artery walls help maintain the flow of blood away from heart
    • Prevents backflow so no valves are needed
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The circulatory system (B-A*)

  • Capillaries form capillary beds in the tissues of the body
  • They provide a large surface area for the efficient exchange of materials between the blood and tissues
  • The blood is at a higher pressure at the artery end of the capillary bed
    • The higher pressure forces plasma through the thin capillary walls
    • The liquid, called tissue fluid, carries nutrients and oxygen to surrounding cells
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