GCSE Combined Science (AQA)

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Diffusion in the Lungs

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Cell Biology Transport in Cells

Diffusion in the Lungs

4:29 Diffusion in Action
Spec 4.1.3.1
Previous Multicellular Organisms Next Diffusion in the Intestines
  • Gases are exchanged in the lungs, involving the absorption of oxygen into the blood and removal of carbon dioxide.
  • The lungs are well ventilated, facilitating air movement in and out through the nose and mouth.
  • Adaptations of mammalian lungs for material exchange include specialized structures like alveoli.
  • Alveoli, located at the end of lung branches, are tiny and numerous, optimized for gas exchange.
  • Oxygen diffuses into the blood due to lower oxygen concentration in blood returning from the body, moving down its concentration gradient.
  • Deoxygenated blood from tissues, low in oxygen and high in carbon dioxide, flows through lung capillaries.
  • Carbon dioxide diffuses from the blood into the alveoli and is then exhaled, following its concentration gradient.
  • The result is oxygen-rich blood, low in carbon dioxide, ready for body tissues.
  • Alveoli have thin, one-cell-thick membranes providing a short diffusion pathway, enhancing the diffusion rate.
  • The large surface area and extensive capillary network around alveoli increase the efficiency of gas exchange.
  • Alveoli's large surface area to volume ratio and rich blood supply maintain a steep concentration gradient, crucial for efficient gas exchange.
  • Understanding these adaptations is essential for explaining how lungs and alveoli function as effective exchange surfaces in exams.

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