Salivary glands functions, types, diseases

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Philip Kelley
Salivary glands functions, types, diseases

The salivary glands They are the organs responsible for the production of saliva. They are exocrine glands and are mainly located in the head and neck regions, where they fulfill different physiological functions in the aerial digestive tract..

These glands, along with the liver and pancreas, are among the most important for the digestive system, where they participate in the digestive process and, therefore, in the maintenance of body homeostasis.

The major salivary glands (Source: CFCF, via Wikimedia Commons)

While the pancreas and liver have endocrine (with products released into the blood) and exocrine (with products released onto a surface) functions, the salivary glands only fulfill exocrine functions, since they function in the production and release of saliva into the oral cavity..

Saliva is essential for digestion, but it is also essential for maintaining the health of the mouth, teeth and other organs associated with this cavity..

Two types of salivary glands have been described, known as "major" and "minor." The larger ones participate in the production of the greatest amount of saliva, but the smaller ones are important because of the saliva products they excrete..

Like any organ in the body, these structures can have pathologies caused by obstructions, infections, tumors or inflammations, which unquestionably affect the health of human beings..

Article index

  • 1 Where are the salivary glands located?
  • 2 Functions
  • 3 Types of salivary glands
    • 3.1 Major salivary glands
    • 3.2 Minor salivary glands
  • 4 Diseases
  • 5 References

Where are the salivary glands located?

Illustration of the mouth and salivary glands

The salivary glands are found in the anatomical regions of the head and neck, specifically inside the oral cavity and its surroundings..

There are very large salivary glands, which are internally, just below each ear, under the tongue and under the jaw.

There are also others much smaller but much more abundant, and these are distributed by the submucosa of the sinus-nasal cavity, the oral cavity, the pharynx, the larynx and the trachea, the lungs and the middle ear; being particularly abundant in the buccal, labial, lingual and palatal mucosa (that of the palate).

Features

The salivary glands are fundamental organs for the maintenance of the internal conditions of the oral cavity.

Its main function, as it can be understood from its name, has to do with the production of saliva, which is a fluid with multiple functions that, together, participate in the maintenance of oral health:

  • Lubricates the oral mucosa.
  • Provides electrolytes and some antibacterial compounds (immunoglobulin A, lactoferrin -which sequesters iron-, lysozyme -which smooths bacteria- and thiocyanate ions -bactericides-).
  • Contains enzymes that protect the oral mucosa and tooth surface.
  • Promotes coagulation and wound healing, as it contains clotting factors and epidermal growth factors.

In addition, saliva is very important during the ingestion of food, because:

  • Participate in the taste sensation.
  • Facilitates the hydration of what is chewed.
  • It contains some enzymes that begin with the digestion of some elements in food such as complex carbohydrates (amylase enzyme) and lipids (lipase enzyme).
  • Provides a kind of vehicle for movement of the food bolus down the throat during swallowing (when swallowed).

Types of salivary glands

The human body has two types of salivary glands known as the major salivary glands and the minor salivary glands..

In general terms, it can be said that these glands are made up of specialized epithelial cells and that they have two functional segments: one that is made up of acinar cells (secretory) and the other of a complex system of ducts and myoepithelial (contractile) cells that favor the secretion into ducts.

Major salivary glands

There are three pairs of major salivary glands: the parotid, the submandibular, and the sublingual. These glands participate in the production of 90% of the total daily saliva.

They are distinguished from the minor glands by the fact that their products reach the oral cavity through long ducts.

Sublingual glands

They are the smallest of the major glands and are found between the connective tissue of the "floor" of the mouth and the mylohyoid muscle, that is, under the tongue, where their excretion products are released..

Submandibular or submaxillary glands

These are the second largest salivary glands in the human body and are located in the submandibular triangle, behind the insertion site of the mylohyoid muscle (on the internal oblique line of the jaw) or, in simpler words, below the jaw..

The excretion products of these glands are discharged into the oral cavity through ducts that open in the “lingual frenulum”, which is the membrane located under the tongue..

The submandibular glands have serous and mucous acinar cells, which are responsible for the production of thick saliva, rich in glycoproteins and growth factors, which participate in the lubrication and protection of the mucosa that lines the mouth on the inside..

Parotid glands

The parotid glands are the largest of the three major salivary glands. They are found on both sides of the head, behind the external ear canal and at the base of the skull (under each ear). Its excretion products reach the oral cavity at the level of the upper molar region..

These glands specialize in the production of a saline aqueous substance, rich in the enzyme amylase and other glycosylated proteins (mucins). They are stimulated by nerves of the sympathetic division of the peripheral nervous system..

Minor salivary glands

The minor salivary glands are those that are interspersed between the intrinsic muscles of the tongue; the oral cavity and all many of its organs have hundreds of these glands, which discharge their contents into this space through small and short ducts.

Their secretions represent less than 10% of the saliva that is produced in the mouth every day, but given their composition they are considered the most important for the protection and lubrication of the oral mucosa, where they also work in the formation of the biofilm dental.

Among some of the main products they excrete are: immunoglobulins, acid phosphatases and lysozymes, which perform fundamental functions in preventing the proliferation of microorganisms.

These glands are found mainly in the oral submucosa -especially in the lips, tongue and palates- but they are also in the sinus-nasal cavity, in the pharynx, larynx and trachea, in the lungs and in the ear cavity. half.

Some examples of these glands are:

- The anterior lingual glands or glands of Blandin-Nuhn, mixed glands that are very close to the tip of the tongue.

- The posterior mucous glands, found in the center of the back third of the tongue.

- The von Ebner glands, some serous glands located on the posterior face of the anterior third of the tongue; their ducts bathe the circumvated papillae and the grooves of the foliate papillae with serous saliva.

Diseases

The salivary glands can suffer from different pathological conditions such as infections and inflammations (sialadenitis), tumors, obstructions, etc..

The most common benign process in the salivary glands is known as sialolithiasis or salivary gland calculus, that it is the formation of "stones" (calcifications) in the submandibular and parotid glands. It can be painful, especially when consuming foods that stimulate saliva production.

There is a condition known as benign pleomorphic adenoma, that it is a non-cancerous tumor that usually affects the parotid and submandibular glands (major glands).

Its removal, if not careful, can lead to damage to the nerve branches that innervate the face and allow movement of the muscles of facial expression, causing paralysis of these.

Mumps is also a common condition of the parotid salivary glands, characterized by viral infections that cause painful inflammation of the glands, which is highly visible on the outside..

References

  1. de Paula, F., Teshima, T. H. N., Hsieh, R., Souza, M. M., Nico, M. M. S., & Lourenco, S. V. (2017). Overview of human salivary glands: highlights of morphology and developing processes. The Anatomical Record, 300 (7), 1180-1188.
  2. Gartner, L. P., & Hiatt, J. L. (2006). Color textbook of histology ebook. Elsevier Health Sciences.
  3. Kessler, A. T., & Bhatt, A. A. (2018). Review of the major and minor salivary glands, part 1: anatomy, infectious, and inflammatory processes. Journal of clinical imaging science, 8.
  4. Kierszenbaum, A. L., & Tres, L. (2015). Histology and Cell Biology: an introduction to pathology E-Book. Elsevier Health Sciences.
  5. Silvers, A. R., & Som, P. M. (1998). Salivary glands. Radiologic clinics of North America, 36 (5), 941-966.

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