Gas exchange surfaces

Trachea:
Tube allowing air to travel to lungs
Rings of cartilage ensure tube remains open
Mucus traps dust and pathogens
Cilia waft mucus to top of trachea
Bronchi:
Thinner walls and smaller diameter than trachea
Bronchioles:
Large number of bronchioles in gas exchange system
Large ones have elastic fibres and smooth muscle
Alveoli:
Alveolar wall is a single layer of squamous (flattened) epithelium
Thin and permeable for easy diffusion
Surrounded by elastic fibres so they can stretch during inhalation
Carbon dioxide diffuses out of the capillaries and into the alveoli while oxygen diffuses from
the alveoli and into the capillaries
Oxygen and carbon dissolve in moisture to exchange occurs in solution


All organisms exchange gases with their environment via diffusion, e.g., aerobic respiration
and photosynthesis.


● The pleural cavity is filled with fluid.
● Bronchioles are made up of alveoli.
● An alveolus is an example of a gas exchange surface.
● The light purple parts are air spaces.
● The darker parts are the wall of the alveolus and capillaries.


alveoli (alveolus - singular)
● Air travels in and out of the alveoli.
● There is a layer of moisture in the alveolus.
● There is a high carbon dioxide level outside the alveoli and a low level inside them.
● Capillary walls are one cell thick, which creates a short diffusion distance.