The nose is an efficient filter.
Most large particles are stopped in it, until they are removed mechanically by blowing the nose or sneezing. Some of the smaller particles succeed in passing through the nose to reach the windpipe and the dividing air tubes that lead to the lungs [ more information about how particles entering the lungs ]. These tubes are called bronchi and bronchioles. All of these airways are lined by cells.
The mucus they produce catches most of the dust particles. Tiny hairs called cilia, covering the walls of the air tubes, move the mucus upward and out into the throat, where it is either coughed up and spat out, or swallowed. The air reaches the tiny air sacs alveoli in the inner part of the lungs with any dust particles that avoided the defenses in the nose and airways. The air sacs are very important because through them, the body receives oxygen and releases carbon dioxide.
Dust that reaches the sacs and the lower part of the airways where there are no cilia is attacked by special cells called macrophages. These are extremely important for the defense of the lungs. They keep the air sacs clean. Macrophages virtually swallow the particles. Then the macrophages, in a way which is not well understood, reach the part of the airways that is covered by cilia.
The wavelike motions of the cilia move the macrophages which contain dust to the throat, where they are spat out or swallowed. Besides macrophages, the lungs have another system for the removal of dust.
The lungs can react to the presence of germ-bearing particles by producing certain proteins. These proteins attach to particles to neutralize them. Dusts are tiny solid particles scattered or suspended in the air.
The particles are "inorganic" or "organic," depending on the source of the dust. Inorganic dusts can come from grinding metals or minerals such as rock or soil. Examples of inorganic dusts are silica, asbestos, and coal. Organic dusts originate from plants or animals. An example of organic dust is dust that arises from handling grain. These dusts can contain a great number of substances. Aside from the vegetable or animal component, organic dusts may also contain fungi or microbes and the toxic substances given off by microbes.
For example, histoplasmosis , psittacosis and Q Fever are diseases that people can get if they breathe in organic that are infected with a certain microorganisms. Dusts can also come from organic chemicals e. However, in this OSH Answers document, we are only considering dust particles that cause fibrosis or allergic reactions in the lungs.
We are not including chemical dusts that cause other acute toxic effects, nor long term effects such as cancer for example. The way the respiratory system responds to inhaled particles depends, to a great extent, on where the particle settles. For example, irritant dust that settles in the nose may lead to rhinitis, an inflammation of the mucous membrane. If the particle attacks the larger air passages, inflammation of the trachea tracheitis or the bronchi bronchitis may be seen.
http://demo.theknowledgeaward.com/modules/interracial/fylo-rencontre-femme-kabyle.php Particles that evade elimination in the nose or throat tend to settle in the sacs or close to the end of the airways. But if the amount of dust is large, the macrophage system may fail.
Dust particles and dust-containing macrophages collect in the lung tissues, causing injury to the lungs. The amount of dust and the kinds of particles involved influence how serious the lung injury will be. For example, after the macrophages swallow silica particles, they die and give off toxic substances. These substances cause fibrous or scar tissue to form. This tissue is the body's normal way of repairing itself. However, in the case of crystalline silica so much fibrous tissue and scarring form that lung function can be impaired.
The general name for this condition for fibrous tissue formation and scarring is fibrosis. The particles which cause fibrosis or scarring are called fibrogenic.
When fibrosis is caused by crystalline silica, the condition is called silicosis. Several factors influence the effects of inhaled particles. Among these are some properties of the particles themselves. Particle size is usually the critical factor that determines where in the respiratory tract that particle may be deposited. Chemical composition is important because some substances, when in particle form, can destroy the cilia that the lungs use for the removal of particles.
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