What is asthma ?

Human lung mainly consists of two components i.e. the airways & the alveoli. Airways are mechanical conduits of the air. Hence the resistance to passage of air through them would depend on their diameter.

The other component i.e. the alveoli are the gas exchange unite. It is here that the blood absorbs oxygen from the air & releases the carbon dioxide produced in the body.

In some people the airways are hyperreactive i.e. they have abnormal sensitivity to various trigger factors. Exposure to these triggers leads to--
Inflammation of the cells in the airways,causing the air tubes to swell.
The muscles around the air tubes tighten.
Cells in the air tubes make more mucus than normal. This mucus is very thick and sticky, and tends to clog up the tubes.

This decreases their diameter & thus the resistance to the passage of air through them. This thus leads to difficulty in breathing.

Asthma home