Just breathe

You breathe over 10,000 litres of air a day (that’s 2200 gallons for my American friends or any time travellers from 1900) even when you don’t run for the bus or climb 10 flights of stairs. With each lungful you also inhale countless microscopic particles of dust, viruses, pollen, chemicals, spores. Some of these are inert but many are potentially harmful, even life threatening. Fortunately our nasal pathway, hairs and snot do an excellent job of filtering out the largest bits. Many of those that enter the mouth get swallowed and dissolved in stomach acid. Our airways are lined with tiny hairs called cilia which are constantly wafting particles back up out of the tubes on a wave of mucus. Despite all these defences, the innermost air sacs of our lungs, the alveoli, are constantly exposed to clouds of danger. The reason they don’t fill up and healthy lungs don’t become clogged and overwhelmed is due largely to alveolar macrophages. These are part of the family of macrophage cells that ingest foreign objects, introduced in Macrophage – rage or sage.

Like their relatives, they can display a range of behaviour. They must be able to recognise and destroy invading pathogens, they absorb pollutants such as cigarette smoke or vehicle emissions. They can detect when the lung is damaged and help to repair it, although the fact they can do this is not justification for people being exposed to some of those avoidable pollutants mentioned above… Like many of the cells in our body, we take them for granted at our peril. They have enough to do keeping us protected from the normal stresses of being alive without adding to their workload.

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