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Alveoli structure
-100-300µm
-Small, air-filled sacks
-Exchange takes place at walls
-Surrounded by capillaries
-Thin endothelium
Adaptions to reduce diffusion distance (alveoli)
-Capillary wall = 1 cell thick
-Both walls = squamous cells
-Capillaries = close contact with the alveolus walls
-Capillaries are narrow so that the red blood cells (erythrocytes) are squeezed against the capillary wall, making them closer to the air in the alveoli and reducing the rate at which they flow past in the blood.
-Total barrier to diffusion is only 2 flattened cells thick and is less than 1µm thick.
How does the diaphragm and intercostal muscles help with the exchange of gases?
-Briefly-
remove dust, bacteria, pollen and spores
What does cartilage do?
Holds airways open (during inhalation)
What does smooth muscles do?
-briefly-
Control and constrict the diameter of the airway
What does the elastic fibres do?
recoil, aiding ventilation by helping to expel air
What does haemoglobin (Hb) do?
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