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Biology AS CIE

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  1. 1-cell-structure
    10 主题
  2. 2-biological-molecules
    19 主题
  3. 3-enzymes
    13 主题
  4. 4-cell-membranes-and-transport
    16 主题
  5. 5-the-mitotic-cell-cycle
    8 主题
  6. 6-nucleic-acids-and-protein-synthesis
    9 主题
  7. 7-transport-in-plants
    11 主题
  8. 8-transport-in-mammals
    16 主题
  9. 9-gas-exchange
    6 主题
  10. 10-infectious-diseases
    6 主题
  11. 11-immunity
    10 主题
课 8, 主题 15
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8-1-the-circulatory-system AS the-main-blood-vessels

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Exam code:9700

The main blood vessels

  • The pulmonary and systemic circulations are features of a double circulatory system, where blood passes through the heart twice in one full circuit around the body

    • The pulmonary circulatory system transports deoxygenated blood to the lungs for gas exchange

    • The systemic circulatory system transports oxygenated blood to the rest of the body

  • The diffusion of oxygen is reliant on:

    • The concentration gradients that exists between oxygen in the air in the alveoli of the lungs and oxygen in the blood (net diffusion into red blood cells)

    • The concentration gradient that exists between oxygen in red blood cells and the respiring tissues of the body (net diffusion into the mitochondria of cells)

Blood vessel

Systemic / Pulmonary circulation

Carries blood from

Carries blood to

Blood

Pulmonary artery

Pulmonary

Heart

Lungs

Deoxygenated

Pulmonary vein

Pulmonary

Lungs

Heart

Oxygenated

Aorta

Systemic

Heart

Rest of the body

Oxygenated

Vena cava

Systemic

Rest of the body

Heart

Deoxygenated

Worked Example

An endothelial layer of squamous cells line every blood vessel.

Which of the following is not an advantage provided by this layer of cells?

  1. Reduction in friction

  2. Resisting increases in blood pressure

  3. Increased elasticity of the vessel

  4. Reduced damage to the blood vessel

The correct option is 3, as the squamous epithelial cells do not increase elasticity.

Examiner Tips and Tricks

Remember that although large blood vessels carry blood at a faster rate, their overall surface area in the body is much smaller in comparison to the surface area of capillaries. This is because there are many millions of capillaries in the body.

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