mucus

Mucus is a viscous, gel-like secretion produced by the mucous membranes that line many parts of the body, including the respiratory, gastrointestinal, and reproductive tracts. In humans, mucus is generated mainly by goblet cells and by mucous glands in the airways and other mucosal surfaces. It forms a protective layer that covers and lubricates epithelia.

Mucus has multiple components, with water and mucins—the large glycoproteins that give mucus its gel-like consistency—being the most abundant. It also contains electrolytes, lipids, antibodies such as IgA, enzymes, and immune cells. The mucus functions to moisturize and humidify surfaces, trap dust, microbes, and particulates, and facilitate their removal from the body. In the airways, the mucus is moved by cilia in a process called the mucociliary escalator, guiding trapped material toward the throat to be swallowed or expelled.

Secretions vary by location and physiological state. In the gut, mucus protects the epithelium from acid and enzymatic damage and aids lubrication; in the reproductive tract, mucus can influence sperm movement and infection defense. Production is regulated by neural, hormonal, and inflammatory signals, and irritants such as smoke can increase secretion or alter mucus properties. Inflammation can lead to thicker or more copious mucus.

Clinically, mucus properties are often altered in disease. Increased production occurs with infections and allergic responses, while cystic fibrosis and some chronic lung diseases can produce abnormally thick mucus that is harder to clear. Color and viscosity changes can accompany infection or inflammation. Treatments commonly focus on hydration, airway clearance, and, when appropriate, agents that modify mucus properties.