The cold, dry air we breathe in on even the most
bitterly cold winter's day will have been transformed into 'tropical'
air by the time it reaches the lungs. Here is an example of
the ability of the nose to heat and humidify the air we inhale:
The viscous layer of mucous secreted by the nasal
mucous membrane is there to intercept and exclude solid matter
in the air we breathe (dust, pollen, bacteria, viruses etc.).
The surface of the membrane is covered with countless cilia,
tiny hair-like cell structures which normally undulate at the
rate of 1200 movements per minute to keep the mucous moving
towards the pharynx. Within the cells there is constant biochemical
activity, in effect a detoxification process.
