Difference Between Mucus and Phlegm

Main Difference – Mucus vs Phlegm

Mucus and phlegm are two types of secretions in the airways of animals. Both mucus and phlegm are produced by the epithelium of the airways. Moreover, mucus is also produced by the eye, nasal turbinate as well as the urogenital tract. The main difference between mucus and phlegm is that mucus serves as the regular protective layer of the airways whereas phlegm is produced during inflammation and diseases in the airways. Phlegm consists of bacteria, virus, and other debris.

Key Areas Covered

1. What is Mucus
– Definition, Composition, Role
2. What is Phlegm
– Definition, Composition, Role
3. What are the Similarities Between Mucus and Phlegm
– Outline of Common Features
4. What is the Difference Between Mucus and Phlegm
– Comparison of Key Differences

Key Terms: Airways, Glycoprotein, Inflammation, Mucus, Pathogens, Phlegm

What is Mucus

Mucus refers to a slippery secretion from the lining of the mucous membranes. It is a colourless, slippery fluid produced by the epithelial linings of the body. Mucus is composed of 95% water, 3% proteins, and 1% salts. Before the release of the mucus from the mucous glands, the mucin droplets swell by absorbing water. The strands of mucus are formed by cross-linking, producing a sticky, elastic gel. Generally, the human body produces about 1 – 1.5 litres of mucus per day. The mucus becomes noticeable only when the production is increased due to different illnesses. The function of mucus layer of the respiratory epithelium is shown in figure 1.

Figure 1: Mucus Layer

The two basic functions of mucus are to provide protection and lubrication. The mucus layer serves as a physical barrier to most pathogens. The constant flushing movement of the mucus prevents the establishment of bacterial biofilms. Mucus also traps dust and smoke. Mucus secretions provide lubrication and serve as a moisturizing layer, preventing the drying out of the organs.

What is Phlegm

Phlegm refers to a thick, viscous substance secreted by the mucous membrane of the respiratory passage. It is only found in mammals. Phlegm mainly refers to the secretions that come from the back of the throat or lungs. Hence, the mixture of phlegm and saliva expelled from the nasal passages by coughing is known as sputum. Phlegm may consist of glycoproteins, lipids, immunoglobulins, pathogens such as bacteria and virus, and sloughed-off inflammatory cells. Figure 2 shows a sputum sample containing Mycobacterium tuberculosis.

Figure 2: A Sputum Sample Containing Mycobacterium Tuberculosis

Generally, phlegm is produced as a response to an infection. The composition of the phlegm depends upon genetics, climate, and the state of the immune system. Phlegm can be thin or thick, watery or sticky. The colour of the phlegm depends on the type of infection. Phlegm is mainly produced during common cold and allergies.

Similarities Between Mucus and Phlegm

Mucus and phlegm are two types of secretions in the airways of animals.
The composition of both mucus and phlegm is similar.
Both mucus and phlegm are involved in the protection of the cavities of the airway from foreign particles.

Definition

Mucus: Mucus is a slippery secretion produced by the lining of the mucous membranes.

Phlegm: Phlegm is a thick, viscous substance secreted by the mucous membrane of the respiratory passage of mammals.

Production

Mucus: Mucus is produced by the lining of the airways, eye, nasal turbinate, urogenital tract, and the anus.

Phlegm: Phlegm is produced by the lining of the airways.

Types of Animals

Mucus: Mucus is produced by both vertebrates and invertebrates.

Phlegm: Phlegm is produced by mammals.

Significance

Mucus: Mucus is produced as the regular protective layer of the airways.

Phlegm: Phlegm is produced during inflammation.

Texture

Mucus: Mucus is a colourless, adhesive, viscous gel.

Phlegm: Phlegm is a thin or thick, watery or sticky, and coloured secretion.

Function

Mucus: Mucus provides both protection and lubrication.

Phlegm: Phlegm provides protection from the foreign materials.

Conclusion

Mucus and phlegm are two types of secretions produced by the epithelial layer of the organs. Mucus refers to the regular secretions of the epithelial layer that is thin and slippery. The main function of mucus is to act as a protective barrier against foreign particles. It also lubricates the body surfaces. However, phlegm is a secretion produced in response to infections. It is thick and coloured. It provides protection against pathogens. The main difference between mucus and phlegm is the texture and the function of each type of secretions.

Image Courtesy:

1. “Blausen 0766 respiratory epithelium” By Blausen.com staff (2014). “Medical gallery of Blausen Medical 2014”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. – Own work (CC BY 3.0) via Commons Wikimedia
2. “TB in sputum” – The original uploader was TimVickers at English Wikipedia – This media comes from the Centers for Disease Control and Prevention’s Public Health Image Library (Public Domain) via Commons Wikimedia

Reference:

1. Dunleavy, Brian P. “What Is Mucus?” EverydayHealth.com, 19 Apr. 2016, Available here.
2.“How To Get Rid Of Phlegm.” How To Get Rid Of Phlegm, Available here.