Difference Between Serous and Mucous

Main Difference – Serous vs Mucous

Salivary glands are a type of exocrine glands, which secrete saliva in response to the nerve impulses of the parasympathetic nervous system. Serous and mucous are the two types of glands which make up salivary glands. Serous and mucus are the two secretions of the serous and mucous glands, respectively. There are three types of salivary gland pairs as parotid, submandibular, and sublingual glands. The parotid gland only secretes serous. Both submandibular and sublingual glands secrete serous and mucus. The main difference between serous and mucous is that serous gland secretes a thin, watery secretion containing zymogens, antibodies, and inorganic ions, which are mainly involved in digestion and defense whereas mucous gland secretes a thick, viscous secretion, containing mucin, which is mainly involved in lubrication.

Key Areas Covered

1. What is Serous
      – Definition, Glands and Secretion, Function
2. What is Mucous
      – Definition, Glands and Secretion, Function
3. What are the Similarities Between Serous and Mucous
      – Outline of Common Features
4. What is the Difference Between Serous and Mucous
      – Comparison of Key Differences

Key Terms: Acini, Alpha-Amylase, Mucin, Mucous, Mucous Gland, Parotid Glands, Serous, Serous Gland, Sublingual Glands, Submandibular Glands, Zymogens

What is Serous

The serous is a type of gland found in salivary glands, producing a protein-rich fluid with digestive enzymes. The serous is composed of clusters of cells called acini. The cells in these clusters contain round, central nuclei. All of the three salivary glands, parotid, submandibular, and sublingual glands contain serious glands. Parotid gland only contains serous glands. Submandibular and sublingual glands contain both serous and mucous glands. The serous glands contain large striated ducts.

Figure 1: Serous glands

The secretion of the serous gland is isotonic with the blood plasma. It contains zymogens, antibodies, and inorganic ions. The main function of the secretions of the serous glands is to solubalize dry food, maintain oral hygiene, and initiate starch digestion. The alpha-amylase in the serous secretion breaks down starch into maltose. The serous glands in the papilla foliata are shown in figure 1. 

What is Mucous

The mucous is a type of gland found in salivary glands, producing a slippery solution with mucus. The cells in the mucous glands are arranged into clusters called mucous acini. The mucous cells in the acini comprise flattened nuclei against the basement membrane. Submandibular and sublingual glands contain mucous glands. The mucous glands contain small striated ducts.

Figure 2: Mucous (Left) and Serous (right) glands

The secretion of the mucous glands is a thick solution containing a lot of mucus. The main function of the mucous secretions is to lubricate the oral cavity and make food into the slippery bolus. Both serous and mucous glands are shown in figure 2.   

Similarities Between Serous and Mucous

• Serous and mucous are two types of glands, which make up the salivary glands.
• Both are exocrine glands, stimulated by the parasympathetic nervous system.
• Both serous and mucous glands comprise acinar epithelial cells.
• Secretions of both glands are involved in lubrication, solubilizing dry food, and oral hygiene.

Difference Between Serous and Mucous

Definition

Serous: Serous gland is a constituent of salivary glands, producing a solution with proteins in an isotonic watery fluid.

Mucous: Mucous gland is a constituent of salivary glands, producing a slippery, aqueous secretion.

Nature of the Secretion

Serous: Serous produces a thin, watery secretion, comprising zymogens, antibodies, and inorganic ions.

Mucous: Mucous produces a thick, viscous secretion, comprising of mucin.

Nuclei of the Cells

Serous: The cells that make up the serous glands contain round, central nuclei.

Mucous: The cells that make up the mucous glands contain flattened nuclei against the basement membrane.

Chromatin

Serous: The cells in the serous glands contain dispersed chromatin.

Mucous: The cells in the mucous glands contain condensed chromatin.

Staining with H&E

Serous: Serous glands are stained in dark due to the presence of zymogens.

Mucous: Mucous glands are stained in light due to the presence of mucin.

Ducts

Serous: Serous glands contain large, striated ducts.

Mucous: Mucous glands contain small, striated ducts.

Function

Serous: The serous secretions are involved in solubilizing dry food, maintaining oral hygiene, and initiating starch digestion.

Mucous: The mucous secretions are involved in lubricating the oral cavity and making food into the slippery bolus.

Conclusion

Serous and mucous are two types of glands, which collectively make up the salivary glands. Serous glands secrete a protein-containing solution, which is involved in digesting starch and protecting oral cavity from pathogens like bacteria. Mucous glands secrete a thick solution with mucus, which is involved in lubricating food and oral cavity. Thus, the main difference between serous and mucous is in the composition of each secretion and their function in the oral cavity.

Reference:

1. “Salivary Glands and Saliva.” VIVO Pathophysiology. N.p., n.d. Web. Available here. 09 July 2017. 

Image Courtesy:

1. “Gray1021” By Henry Vandyke Carter – Henry Gray (1918) Anatomy of the Human Body (See “Book” section below)Bartleby.com: Gray’s Anatomy, Plate 1021 (Public Domain) via Commons Wikimedia
2. “Gray1026” By Henry Vandyke Carter – Henry Gray (1918) Anatomy of the Human Body (See “Book” section below)Bartleby.com: Gray’s Anatomy, Plate 1026 (Public Domain) via Commons Wikimedia

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