Lung function

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  • Created by: Rachh
  • Created on: 07-01-13 13:13
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  • The lungs
    • Structure
      • Air enters the trachea.
        • The trachea splits into two bronchi.
          • Each bronchus branches off into smaller tubes called bronchioles.
            • The bronchioles end in small air sacs called alveoli, where gas exchange takes place.
    • Ventilation
      • Inspiration
        • The intercostal and diaphragm muscles contract.
          • This causes the ribcage to move upwards and outwards and the diaphragm to flatten, increasing the volume of the thorax.
            • As the volume of the thorax increases, the lung pressure decreases.
              • This causes air to flow into the lungs.
        • It is an active process - it requires energy.
      • Expiration
        • The intercostal and diaphragm muscles relax.
          • The ribcage moves downwards and inwards and the diaphragm becomes curved again.
            • The thorax volume decreases, causing the lung pressure to increase.
              • Air is forced out of the lungs.
        • It is a passive process - it doesn't require energy.
    • Alveoli and gas exchange
      • Factors affecting the rate of diffusion
        • A thin exchange surface (short diffusion pathway)
        • A large surface area - lots of very small alveoli means there's a large surface area for gas exchange.
        • A steep concentration gradient of oxygen and Carbon dioxide.
      • Alveoli structure
        • Each alveolus is made from a single layer of thin, flat cells called the alveolar epithelium.
        • The walls of the capillaries are made from capillary endothelium.
        • The walls of the alveoli contain a protein called elastin.
          • Elastin is elastic - it helps the alveoli return to their normal snap after inhaling and exhaling air.
      • Gas exchange in the alveoli
        • Oxygen diffuses out of the alveoli and into the haemoglobin in the blood.
        • Carbon dioxide diffuses into the alveoli from the blood and is breathed out.
  • Air is forced out of the lungs.
  • It is a passive process - it doesn't require energy.
  • A steep concentration gradient of oxygen and Carbon dioxide.
  • Alveoli and gas exchange
    • Factors affecting the rate of diffusion
      • A thin exchange surface (short diffusion pathway)
      • A large surface area - lots of very small alveoli means there's a large surface area for gas exchange.
    • Alveoli structure
      • Each alveolus is made from a single layer of thin, flat cells called the alveolar epithelium.
      • The walls of the capillaries are made from capillary endothelium.
      • The walls of the alveoli contain a protein called elastin.
        • Elastin is elastic - it helps the alveoli return to their normal snap after inhaling and exhaling air.
    • Gas exchange in the alveoli
      • Oxygen diffuses out of the alveoli and into the haemoglobin in the blood.
      • Carbon dioxide diffuses into the alveoli from the blood and is breathed out.

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