Page 115 - Advanced Mine Ventilation

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Figure 7.1 The human respiratory system.

called cilia, which trap and transport to the mouth any insoluble particle deposited in
that region. These particles are spat, sneezed out, or swallowed. Because the digestive
system is much sturdier than the respiratory system, the swallowed particles seldom do
any harm. Particles deposited in the alveoli and alveolar sacs are ingested by migratory
cells, the phagocytes, and transported to lymph nodes to be eventually rejected through
the body waste disposal system.
Notwithstanding the protective mechanism outlined earlier, deposition of dust in
lungs builds up with continued breathing in dusty air, which leads to the breakdown
of the elimination system and pathological harm ensues. In the earlier stages of the dis-
ease, the dust particles accumulated in the lymph nodes produce local inflammation.
This is known as simple pneumoconiosis, and given better environment at this stage,
a victim can recuperate in time. Continued breathing in the dusty air, however, can
eventually lead to the fibrosis of the lung tissues. A tissue affected by fibrosis subse-
quently enlarges and coalesces to form a dense mass of fibrous tissues. The alveolar