mucous

Mucous is an adjective used to describe anything relating to mucus or to mucous membranes. The noun most often used for the slippery secretion itself is mucus. In common usage, mucous appears in phrases such as mucous membranes or mucous secretions, while the substance is usually called mucus.

Mucus is a viscid, gelatinous secretion produced by goblet cells and mucous glands located on mucous membranes. It is composed primarily of water, glycoproteins (mucins), electrolytes, enzymes, antibodies, and lipids. Mucus is continually produced in many parts of the body, especially along the respiratory, gastrointestinal, reproductive, urinary tracts, and on ocular surfaces.

The functions of mucus include lubricating and protecting surfaces, trapping dust, microbes, and particulates, and facilitating their removal. In the respiratory tract, mucus works with cilia in the mucociliary escalator to move trapped material upward and outward. The viscosity and volume of mucus can vary with hydration, health, and environmental factors, and abnormalities can occur in disease.

Clinical relevance varies with conditions that affect mucus production or clearance. Excessive or thickened mucus can contribute to nasal congestion, bronchitis, and other respiratory illnesses, and is a feature of cystic fibrosis, chronic obstructive pulmonary disease, and allergic or inflammatory conditions. Dryness of mucous membranes can occur with dehydration, Sjögren syndrome, or certain medications. Treatment aims to maintain hydration, humidify airways, and facilitate mucus clearance through saline irrigation, expectorants, or mucolytics, along with management of underlying disorders.