Animation: asthma attack
Phases of an asthma attack
Airborne allergens, such as pet dander (hair and skin flakes), pollen or house dust mite faeces, are breathed into the lungs nearly every day by most of us.
A close-up of a normal airway is shown first. The airway, or lumen, (centre black part) is fully open and there is just a thin coating of mucus on the inside of the airway (yellow). The inner lining of the airway (pale pink) is in its normal state.
In people with asthma, inhaled allergens can trigger an asthma attack.
Three processes can occur in the airway during an asthma attack. They all contribute to a narrowing of the airway.
- The muscle wall of the airway (purple outside layer) contracts (squeezes), reducing the overall size of the lumen.
- There is an increase in secretion of mucus (yellow), which further blocks the airway.
- The inner lining of the airway becomes inflamed and swells, adding to further narrowing of the airway.
The resulting narrowing of the airways in the lungs (see the final image) makes breathing difficult and the inflammation of the airways can make them super-sensitive to irritants.
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Last Reviewed: 07 February 2005
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