Looking at the Gas Exchange under the Microscope (AQA AS Biology): Revision Note

Examining gas exchange surfaces

• School students may use pre-prepared microscope slides to view gas exchange tissue under an optical microscope

Mammalian gas exchange tissue

• Thin sections of mammalian lung tissue may display the following features:

  • alveoli that differ in size and shape

  • alveolar walls that are:

    • one cell thick

    • made up of flattened cells

  • nuclei that are shown as dark dots

  • blood vessels in between the alveoli

Fish gas exchange tissue

• Thin sections of fish gill tissue may display the following features:

  • the gill arch which provides a backbone for the gill filaments

  • many filaments arranged along the gill arch

  • lamellae visible at higher power

Insect gas exchange tissue

• Electron microscopes can take clear images of insect gas exchange structures, e.g. the spiracles

Dicotyledonous leaves

• A section of stained tissue from a dicotyledonous leaf can allow the following features to be viewed:

  • waxy cuticle

  • epidermal layers

  • palisade mesophyll layer

  • spongy mesophyll layer

  • stomata

  • guard cells