What Are Mucous Membranes?

Mature man hydrates with home humidifier.
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Also known as: mucosa, mucosae, mucosal tissue

Mucous membranes protect the inside parts of your body that are exposed to air, in a similar fashion to how your skin protects your external body. Examples of mucous membranes includes: 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).

 Mucous membranes are rich with mucous glands that secrete mucus to help keep the membranes moist.  

The human body has 4 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 covers and protects underlying connective tissue (fibrous and elastic tissue built for supporting other structures of the body). 

Mucous Membranes of the Ears, Nose & Throat

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

Oral mucous membranes are reddish pink and line the inside of the mouth. 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 are lined with small blood vessels that help to warm and humidify the air you breath. The mucous membranes are also lined with cilia, tiny hair-like structures, that help to trap debris that you breath in. The cilia then move the debris either towards the front of your nose or towards the back of the throat.

Mucous membranes of the ears are the first line of defense for the middle ear, which is normally bacteria free. Like the nasal mucous membranes, mucosa in the ears have cilia which move any debris towards the opening of the eustachian tube. The eustachian tube likewise has mucous membranes with cilia to transport the debris toward the back of the throat to be swallowed, protecting the middle ear from acquiring an infection. The mucous membranes in the middle ear also secrete cells from the immune system, which may be why otitis media with effusion (fluid in the ear) does not always cause an infection.

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 foods movement. The mucous membranes in the esophagus also contain minor salivary glands which 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. There is some belief that the mucous membrane starts to thin with advanced age, however this does not have much supporting research.

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. A thorough oral exam may help tip your doctor off as to what problem you may be having. 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 syndrom, or Addison disease
  • gastrointestinal - Crohn 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.

Source:

Islam, NM, Bhattacharyya, I & Cohen, DM. (2011). Common Oral Manifestations of Systemic Disease. Otolaryngologic Clinics of North America. 44(1). 161-182.

Lim, D.J. (1976). Functional morphology of the mucosa of the middle ear and Eustachian tube. Ann Otol Rhinol Laryngol. (2 Suppl 25 Pt 2):36-43.

National Cancer Institute. SEER Training Modules: Membranes. Accessed: December 14, 2010 from http://training.seer.cancer.gov/anatomy/cells_tissues_membranes/membranes.html

Nelson, L.P. (n.d.). Biology of the Mouth. Accessed on 2/28/2016 from http://www.merckmanuals.com/home/mouth-and-dental-disorders/biology-of-the-mouth-and-teeth/biology-of-the-mouth

Squier, C.A. & Kremer, M.J. (2001). Biology of oral mucosa and esophagus. J Natl Cancer Inst Monogr. (29): 7-15.

Tucci, D.L. (n.d.). Nose and Sinuses. Accessed on 2/28/2016 from http://www.merckmanuals.com/home/ear,-nose,-and-throat-disorders/biology-of-the-ears,-nose,-and-throat/nose-and-sinuses

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