Mucous Membrane: Definition, Structure, Functions and Impact

Mucous membrane is also called mucosa which is a smooth tissue that traces the digestive, respiratory, and reproductive structures of our body. The 3 layers present in mucosa are epithelium, lamina propria, and muscularis mucosae respectively. Immunity is notably motivated through it. 

• It performs an essential function in protection of our frame together with White Blood Cells and it additionally allows indigestion.
• Mucous membrane helps in keeping the underlying tissues moist.
• Mucous membrane contains cells which are adapted for absorption and secretion.
• The principal constituent of mucus membrane is called mucin.

Key Terms: Mucous Membrane, Epithelium Lamina propria, Muscularis mucosae, Pathogens, Mucosa, Immune System, Polyps, Mucus

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What is Mucous Membrane

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Mucous membrane is also known as mucosa. Mucosa is used to line the body cavities and internal organs.

• Mucous membrane lubricates the organs and cavities and also shields them from invasive microorganisms as well as abrasive particles and bodily fluids. 
• The body's largest barrier of defense is made up of mucosa. It also plays a part in absorption in the gastrointestinal tract where it helps in digesting.
• The main function of mucous membranes and the mucus is to provide protection and lubrication. 
• For instance, particles and pathogens (organisms that cause disease) get caught in produced mucus and are unable to enter deeper tissues, such as the lungs (in the case of the respiratory tract) or tissues that are directly below the membrane layer. 
• The mucus and membranes also maintain the moisture of the underlying tissues.

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Mucosa Composition

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Three layers make up the mucosa:

1.  Epithelium

The outer layer of mucosa is known as the epithelial layer. Mucosa get's it name from the thick, gel-like mucus that epithelial cells secrete to shield the body from irritants.

• Because different sections of the body require different arrangements of the cells. 
• Cells may be piled in columns or set out like bricks, and there may be one or many layers of them. 
• The cells replace themselves while removing the particles invading inside. Hence, have a high cell turnover rate. 
• CIlia is also present which are tiny hairs that help in the removal of the foreign particles.

2. Lamina propria

Lamina propria is defined as the connective tissue where the epithelium is attached. It is the middle layer of the mucosa. 

• Lamina propia is made up of nerves, veins, and structural protein molecules.
• It is used to hold the cells in its position and binds them to the smooth muscle below while supplying blood to the epithelium. 
• The neurons of lamina propria squeeze and stretch in response to changes in muscle tension to alter the epithelium's shape. 
• It supports the immune cells to kill and eliminate infections.

3. Muscularis mucosae

The muscularis mucosae is a layer of smooth muscle and is the deepest layer of mucosa. It has thick parts in different parts of the digestive tract, although it is most active in the stomach. 

• The mucosa is seemed to be in motion by a constant motor function which is being provided by the muscularis mucosae.
• It makes it easier for the mucosa to expand and contract when the organs of the digestive system are working. 
• By maintaining the action of the surface's hair-like cilia, it also assists the mucosa in carrying out its cleansing duties.

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Function of Mucous Membrane

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The human body depends heavily on the mucous membrane. The following is a list of some of the mucous membrane's crucial roles:

• The mucous membrane and mucus primary job is to keep the tissue wet (for example in the respiratory tract, including the mouth and nose).
• The lining of the eye's mucous membrane is crucial for the transformation and absorption of nutrients.
• Mucosa in the stomach protects against stomach acid and in the bladder shields the underlying tissue from urine, mucous membranes likewise shield the body from potentially dangerous substances.
• Mucous membrane of the endometrium in the uterus swells each month and is expelled during menstruation.

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Mucous Membrane Location

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Human body contains mucous membranes in every of the systems like the digestive system, respiratory system, reproductive system, and sensory organ systems.

• Body cavities with mucous membranes can be found in your Nostrils, Mouth, Throat, Ears, Genitals and Anus.
• Your body's hollow organs with mucosa include Esophagus, Lungs, Stomach, Intestines, Bladder and Uterus.

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Disease of Mucous Membrane

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The mucosa is made to protect against abrasion and infection, yet occasionally something can get past its barriers. Viruses, fungi, and bacteria can harm the mucous membranes of your mouth, genitalia, and occasionally, your digestive system.

• Herpes genital and oral.
• Yeast infections in the genitalia and oral thrush.
• Oral and genital lichen planus
• Bullous pemphigus oropharynx.
• Pemphigus oral.
• Mouth ulcers
• Mononucleosis.
• HPV infection of the oropharynx.
• Mouth, foot, and hand illness.
• H. pylori contamination

The immune system reacts when something pierces mucosa. When the respiratory system creates more mucus to fend against a cold or an allergen the tissues inside the organs swell up. Even though inflammation is a healthy reaction to an injury or infection, it can cause unpleasant symptoms.

Among the mucosal disorders that cause inflammation are:

• Gastritis.
• Cystitis.
• Cervicitis.
• Cholecystitis.
• Esophagitis.
• Bronchitis.
• Sinusitis.
• Gastroenteritis.
• Proctitis.
• Syndrome of Zollinger-Ellison.
• Stomach ulcer illness.
• Asthma.
• Leukoplakia.

An unsuitable immune response occasionally results from autoimmune disorders in the mucosa. They trigger the body to mistake healthy cells for infections, which results in persistent inflammation. Instances that can harm the mucosa include:

• Celiac illness.
• Bowel inflammation conditions.
• Behcet's illness.
• Autoimmune pancreatitis.
• Auto-immune hepatitis

Long-term inflammation has the potential to lead to fibrosis, a kind of tissue scarring. Tissue remodeling is another name for this. Remodeling of the mucosa is linked to a number of progressive diseases, such as:

• Esophageal Barrett's.
• Esophagitis with eosinophilia.
• Digestive tract metaplasia.
• The Ménétrier illness.
• Crohn's illness.
• Sarcoidosis.

Sometimes, due to inflammation, tissue remodeling, cancer, or other reasons, the mucosa develops aberrant tissue growths. Polyps are abnormal tissue growths that are often benign but can occasionally be precancerous.

Some of the mucosa polyps are:

• Abdominal polyps.
• Pelvic polyps.
• Polyps in the colon.
• Polyps in the gallbladder
• Nose growths.
• Polyps in the cervix.

The mucosa may malfunction as a result of other disorders.

Mucosa can become dysfunctional due to the following diseases:

• A condition known as endometriosis causes the uterine mucosa to protrude outside of the uterus.
• A disorder called cystic fibrosis makes your respiratory mucosa thicken and obstruct your airways.
• Sjogren's syndrome is an autoimmune condition that targets the glands in your mucosa that secrete mucus, causing dryness.
• Rectal prolapse is a condition where the rectum's mucus lining escapes the anus.
   

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How can mucous membranes be protected?

Mucous membranes defend when everything is working as it should, acting as a first line of protection against abrasion and infection. 

If persistent, chronic inflammation can start to undermine this defense and exhaust the immune cells in mucosa, weakening the immune system.

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Things to Remember

• The mucosa is the soft tissue that lines the digestive, respiratory, and reproductive systems of the body.
• The epithelium, lamina propria, and muscularis mucosae are the three layers of mucosa.
• Mucous membranes can be found in your Nostrils, Mouth, Throat, Ears, Genitals and Anus.
• One of the human body's five sensory organs is the skin. Mucous membranes line the interior surfaces of the body's organs to provide protection.
• The mucous membrane also aids in protecting, supplying these organs and tissues with nourishment.
• Mucous membrane assist in transferring nutrients to the tissues as well as maintaining the tissues' moisture levels