What Causes Mucus?

Mucus, also known as phlegm when it is produced in the respiratory system, is a viscous and slimy substance that serves various important functions in the body. It is produced by specialized cells in different tissues and organs throughout the body. The main causes and functions of mucus production include:

  • Respiratory System:
    • Airway Protection: In the respiratory system, mucus is primarily produced by goblet cells in the lining of the airways (trachea, bronchi, and bronchioles) and the nasal passages. It helps trap and remove airborne particles, such as dust, allergens, and microorganisms, preventing them from reaching the lungs.
    • Moistening and Humidification: Mucus helps maintain the moisture and humidity of the airways, which is essential for proper lung function and the protection of delicate lung tissue.
  • Digestive System:
    • Gastrointestinal Protection: The digestive system also produces mucus to protect the mucous membranes of the stomach and intestines from the harsh acidic environment and the mechanical action of food. The stomach lining, in particular, has specialized cells that secrete mucus to prevent self-digestion by stomach acid.
    • Lubrication: Mucus in the digestive system facilitates the movement of food through the esophagus and intestines, ensuring that it is easily transported and mixed with digestive enzymes.
  • Reproductive System:
    • Cervical Mucus: In the female reproductive system, the cervix produces cervical mucus, which undergoes changes in consistency and composition during the menstrual cycle. Cervical mucus plays a role in sperm transport and fertility by facilitating or impeding the passage of sperm through the cervix.
  • Protection of Mucous Membranes:
    • Eye Lubrication: The eyes produce tear fluid, which contains mucus, to maintain moisture and protect the sensitive cornea and conjunctiva.
    • Oral Health: Saliva contains mucus that helps protect and lubricate the oral cavity, facilitating speech and swallowing.
    • Ear Wax: Earwax, produced by ceruminous glands in the ear canal, is a mixture of mucus and other substances that helps protect the ear canal from foreign particles and bacteria.
  • Immune Response:
    • Infection Defense: When the body detects the presence of pathogens, such as bacteria or viruses, the immune system can trigger the production of mucus to help trap and eliminate these invaders from the respiratory system.
  • Hydration and Maintenance of Tissues:
    • Moisturization: Mucus serves to keep the surfaces of various tissues moist and prevent them from drying out.

The composition of mucus can vary, but it often contains water, glycoproteins, mucins, and electrolytes. Its consistency and function may change in response to different factors, such as infection, allergies, or dehydration. Excessive mucus production or changes in mucus consistency can be indicative of underlying health conditions or infections, and they may be a symptom that warrants medical attention.