From Encyclopedia Jr, free information reference for Kids

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.

Mucus serves many different functions within the processes in an animal's body:

[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] During illness

Generally mucus is clear and thin, serving to filter air during inhalation. During times of infection, mucus can change color 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 color 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] References

• Article from the University of Arizona campus health services
• Everything2.com article on mucus color

[edit] See also

• Nose-picking
• Phlegm
• Empty nose syndrome
• Spinnbarkeit
• Cystic Fibrosis