Mucus
From Wikipedia, the free encyclopedia
Mucus is a slippery secretion of the lining of various membranes in the body (mucous membranes). It is a viscous colloid containing antiseptic enzymes (such as lysozyme) and immunoglobulins. Mucus is produced by goblet cells in the mucous membranes that cover the surfaces of the membranes. It is made up of mucins and inorganic salts suspended in water. Phlegm is a type of mucus that is restricted to the respiratory tract, while the term mucus refers to secretions of the nasal passages as well.
Mucus serves many different functions within the processes in an animal's body:
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[edit] Respiratory system
In the respiratory system, it catches unknown matter and tries to prevent it from entering the body, especially in the nose. Mucus aids in the protection of the lungs by trapping foreign particles that enter the nose during normal breathing. Additionally, it prevents tissues from drying out.
Increased mucus production in the respiratory tract is a symptom of many common diseases, such as the common cold. The presence of mucus in the nose and throat is normal, but increased quantities can impede comfortable breathing and must be cleared by blowing the nose or expectorating phlegm from the throat. Among the components of nasal mucus are tears.
Dried nasal mucus (vulgarly or colloquially called "snot", "booger(s)" (US) or "bogey" (UK)) is partially solidified mucus from the nose. Dried nasal mucus forms when the mucus traps dust and other particles in the air. Mucus dries around the particle and hardens, somewhat like a pearl forming in an oyster. Since catching foreign particles is one of the main functions of nasal mucus, the presence of dried nasal mucus is a good indicator of a properly functioning nose.
[edit] Mucin
Mucous is produced by submucosal cells as well as goblet cells in the respiratory system. It consists of mucin, a highly glycolsilated peptide. Upon stimulation, MARPKs (myrastine-alanine rich protien kinases) signal the binding of mucin filled vesciles to the plasma membrane. The fusion of the vesciles causes the release of the mucin, which as it exchanges Ca2+ for Na+ expands up to 600 fold. The result is a viscoelastic product of interwoven molecules called mucous.
[edit] Digestive system
In the digestive system, mucus is used as a lubricant for materials which must pass over membranes, e.g., food passing down the esophagus. A layer of mucus along the inner walls of the stomach is vital to protect the cell linings of that organ from the highly acidic environment within it.
[edit] Reproductive system
In the reproductive system, cervical mucus prevents infection and helps the movement of the penis during sexual intercourse. When thin, cervical mucus helps the movement of spermatozoa.
[edit] Diseases involving mucus
Generally mucus is clear and thin, serving to filter air during inhalation. During times of infection, mucus can change colour to yellow or green either as a result of trapped bacteria, or due to the body's reaction to viral infection.
In the case of bacterial infection, the bacterium become trapped in already clogged sinuses, breeding in the moist, nutrient-rich environment. In this case, the clogged sinuses are a result of some other condition (such as allergies) and the bacterial infection is secondary to this original cause. When two different colours of common bacteria become mixed (such as yellow Staphylococcus aureus and blue Pseudomonas pyocyanea) the resulting shade is often green. Antibiotics may be used fruitfully to treat the secondary infection in these cases, but will generally not help with the original cause.
In the case of a viral infection such as cold or flu, the first stage of infection causes the production of a clear, thin mucus in the nose or back of the throat. As the body begins to react to the virus (generally one to three days), mucus thickens and may turn yellow or green. In these cases, antibiotics will not be useful, and are a major source of misuse. Treatment is generally symptom-based; the only cure is to allow the immune system to fight off the virus over time.
[edit] Cystic fibrosis
Cystic fibrosis is an inherited disease that affects the entire body, but symptoms begin most the lungs. The lungs become inflamed and produce excess mucus which is difficult to expel.
[edit] Cold weather and mucus
During cold weather, the cilia which normally sweep mucus away from the nostrils and towards the back of the throat (see respiratory epithelium) become sluggish or cease to function completely. This results in mucus running down the nose and dripping (a runny nose). Mucus also thickens in cold weather; when an individual comes in from the cold, the mucus thaws and begins to run again before the cilia begin to work again.
[edit] References
- Article from the University of Arizona campus health services
- Everything2.com article on mucus color
[edit] See also
et:Lima fr:Mucus ja:粘液 pt:Muco pl:Śluz he:ריר sv:Slem yi:שליים
