What Mucous Membranes Do in Your Body

Mucous membranes protect the inside parts of your body that are exposed to air—similar to how your skin protects your external body. Mucous membranes are rich with mucous glands that secrete mucus to help keep the membranes moist.

Examples of mucous membranes include lips, mouth, nasal passages, middle ear, and the eustachian tube. Other mucous membranes include the lining of the digestive tract, the lining of the urogenital tract (including the urethra and vagina), the lining of the respiratory tract, and your eyes (conjunctival membranes).

The human body has four types of tissue with which our organs, bones, cartilage, and other parts of the body are made. One of the types, epithelium, is subdivided into two categories: mucous membranes and serous membranes.

Mucous membranes are made up of epithelial cells that usually cover and protect underlying connective tissue, which is fibrous and elastic tissue built for supporting other structures of the body.

Mucous Membranes of the Ears, Nose, and Throat

Because they are exposed to the outside world, mucous membranes are found in your ears, nose, and throat.

Oral Mucous Membranes

These reddish-pink membranes line the inside of the mouth, and the oral mucosa continues outside the mouth to form the lips.

Because mucous membranes are prone to becoming dry when not adequately hydrated, the lips frequently can become dry. Under normal circumstances, your saliva helps to keep your lips moist.

Nasal Mucous Membranes 

Nasal mucous membranes are lined with small blood vessels that help to warm and humidify the air you breathe. They are also lined with cilia—tiny hair-like structures—which help to trap the debris that you breathe in.

The cilia then move the debris either toward the front of your nose or toward the back of the throat. This is an important function of your immune system, helping to keep harmful germs out of the body.

Mucous Membranes of the Ears

These are the first line of defense for the middle ear, which is normally bacteria free. Like the nasal mucous membranes, these have cilia which move any debris toward the opening of the auditory tube. The auditory tube likewise has mucous membranes with cilia to transport the debris toward the back of the throat to be swallowed.

The middle ear can be affected by allergies and infections, and can fill up with fluid as a result. The fluid can be sterile or infected, and often contains secreted IgA antibodies and white blood cells.

Esophageal Mucous Membranes

Esophageal mucous membranes work in conjunction with a muscular portion to allow for peristalsis, which is the process of moving food toward the stomach. Peristalsis works in a wave-like motion to assist food movement.

The mucous membranes in the esophagus also contain minor salivary glands that secrete bicarbonate in high concentrations. The bicarbonate helps to neutralize any refluxed stomach acid.

Aging and Your Mucous Membranes

Unlike tissue (skin) on the outside of your body, mucous membranes are relatively sheltered from ultraviolet radiation and exposure to the weather. This helps the mucous membranes remain relatively unchanged throughout the aging process.

Mucous membranes also replace themselves quite quickly. However, studies have found that oral mucosa becomes increasingly thin with age.

Oral Mucous Membranes Are the Mirror of the Body

The oral cavity is often referred to as the “mirror of the body,” because the mucous membranes in your mouth change depending on many different diseases.

Changes can be seen in the following types of disorders:

• Hematologic: iron-deficiency anemia
• Autoimmune: Sjögren’s disease
• Pulmonary (lung) diseases: sarcoidosis
• Endocrine: diabetes, thyroid disorders, Cushing’s syndrome, or Addison’s disease
• Gastrointestinal: Crohn’s disease

Caring for Your Mucous Membranes

Dry mucous membranes are a sign of dehydration and can cause various health problems. For example, dry mucous membranes in the lining of the nose can cause frequent bloody noses.

You can help keep your mucous membranes moist by drinking plenty of water. You can also use a humidifier, preferably a cool mist humidifier.