1. Salivary Glands and Tonsils
Chapter 15
Salivary Glands and Tonsils
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2. Salivary Glands and Tonsils
After reading this chapter, the student will be able to:
Discuss the classification of the major and minor salivary glands.
Explain the composition and function of saliva.
Describe the location and purpose of salivary gland duct systems.
Discuss the classification of tonsillar tissue.
Explain the function of the tonsils.
Key terms are important to the understanding of the information in this chapter. Please review and become familiar with them.
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

3. Salivary Glands and Tonsils
Classification of salivary glands
Major salivary glands
Minor salivary glands
Saliva
Myoepithelial cells
Classification of tonsillar tissue
Palatine tonsils
Lingual tonsils
Pharyngeal tonsil
Function of tonsils
Saliva: composition, functions, duct systems.
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4. Classifications of Salivary Glands
Major or minor, depending on their size and the amount of their secretion:
Major glands carry their secretion some distance to the oral cavity by means of a main duct.
Minor glands empty their products directly into the mouth by means of short ducts.
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5. Classifications of Salivary Glands
Cell composition:
Serous cells
Mucous cells
Serous demilunes
Functional unit:
Alveolus or acinus
Serous demilunes is a combination of serous and mucous cells.
Acinus is a cluster of pyramidal cells that secretes into a terminal collecting duct. The collecting duct is known as the secretory end piece or intercalated duct.
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6. Classifications of Salivary Glands
Large glands contain more acini or units arranged in lobules and lobes.
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7. Classifications of Salivary Glands
Serous cells:
High in proteins
Low in carbohydrates
Zymogen granules
Amylase
Mucous cells:
High in carbohydrates
Low in proteins
Mucin
Each type of cell provides a different type of secretion.
Serous cells secrete mostly proteins, small amounts of carbohydrates, and zymogen granules, precursors of the enzyme amylase, which functions in the breakdown of carbohydrates.
Mucin, discharged by mucous cells, is a viscous product that when mixed with watery oral fluids, becomes mucus, causing saliva to be thick and viscous.
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8. Classifications of Salivary Glands
Serous cells and mucous cells are pyramidal.
The nucleus of the serous cell is oval to round.
The nucleus of the mucous cell is oval to spindle-shaped.
The nuclei appear in the basal part of the cell.
The cytoplasm of the serous cell is filled with albumin.
The cytoplasm of the mucous cell appears light and foamy because of the presence of carbohydrates in mucin.
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9. Classifications of Salivary Glands
The serous cell is filled with secretory granules in the apical region, rough-surfaced endoplasmic reticulum, Golgi apparatus, mitochondria, and an oval nucleus.
The mucous cells contain larger droplets of mucin apically and a prominent Golgi apparatus and rough endoplasmic reticulum around the flattened nucleus.
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10. Classifications of Salivary Glands
A third cell type arrangement is a terminal alveolus of mucous cells, with a cap of serous cells. This is called serous demilune, with the secretion of the serous cells passing down a duct between the terminal mucous cells to the lumen of the alveolus.
Salivary glands are termed merocrine glands. The basic mode of product excretion is through membrane vesicles passing to the cell’s apex. These vesicles fuse with the cell plasma membrane and are then exocytosed.
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11. Classifications of Salivary Glands
The serous and mucous cells of the major glands secrete 85% to 90% of saliva. Their combined secretions produce the viscosity and the buffering action of saliva. These properties result from the actions of proteins, carbohydrates, carbonates, and phosphates that are contributed by the secretory ducts of the glands.
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Major Salivary Glands
The major salivary glands are present as three bilateral pairs:
Parotid glands—on the sides of the face, in front of the ears
Submandibular glands—inside the angle of the mandible
Sublingual glands—on either side of the midline, beneath the mucosa of the anterior floor of the mouth
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Major Salivary Glands
Review characteristics of each pair of major salivary glands.
Parotid glands produce a pure serous secretion. Their opening is adjacent to the crowns of the second maxillary molar teeth.
Submandibular glands produce mixed serous and mucous secretion.
Sublingual glands produce nearly pure mucous.
The ducts of the submandibular and sublingual glands share an opening in the anterior floor of the mouth, located at the sublingual papillae on either side of the lingual frenulum.
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Major Salivary Glands
Salivary glands are organized like grapes on a vine. The acini are the grapes. They are arranged in groups or lobules invested in connective tissue. These groups or lobules form larger lobes. The lobes are surrounded by connective tissue containing ducts that drain the glands and the blood vessels and the nerves.
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Minor Salivary Glands
Each minor salivary gland is small, consisting of a cluster of acini, and each is drained by a short duct.
Buccal and labial glands are glands of the cheeks and lips. These mixed glands assist in mastication, swallowing, and speech.
Palatine glands are glands located in the posterior hard palate and the soft palate. In the palate, where keratinized epithelium is present, mucous glands provide adequate lubrication to the epithelium.
Glossopalatine glands are located in the tonsillar folds and are pure mucous glands.
Lingual glands are located in the tongue and are mixed glands at the tongue’s tip.
Serous glands of von Ebner are located at the junction of the tongue’s body and base, where watery secretions washes out the taste buds of the circumvallate papillae.
The tongue also has mucous glands in the posterior region, under the lingual tonsillar tissue.
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Minor Salivary Glands
Review characteristics of each pair of minor salivary glands.
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Saliva Composition
Saliva production is low during sleep and high during stimulation. Saliva flow is generated by taste. Oral and pharyngeal pain and irritation can also induce saliva secretion.
Saliva has fewer proteins and ions than blood. Saliva contains potassium, sodium chloride, calcium, magnesium, phosphorus, carbonate, urea, and traces of ammonia, uric acid, glucose, and lipids.
The major salivary protein is amylase, which is present in the parotid gland and to a lesser extent in the submandibular gland.
Saliva also contains the proteins lysozyme and albumin. Salivary mucin, a mixture of glycoproteins, contributes to the viscous nature of saliva.
Salivary corpuscles are the epithelial cells, leukocytes from the gingival crevices, and the lymphocytes from the tonsils.
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Saliva Functions
To wash the tooth surfaces and prevent the possibility of acid etching
To maintain moisture and protect against irritants and desiccation
To aid in mastication and swallowing
To provide antibacterial action
To assist in pellicle formation
To provide protection in acid-neutralizing and acid-buffering actions
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Saliva Functions
Calcium and phosphate increase enamel hardness and assist in enamel remineralization.
Saliva is necessary for taste.
Salivary proteinslysozymes, lactoperoxidase, and lactoferrinhave antimicrobial properties.
Saliva has antibodies or immunoglobulin such as immunoglobulin A (IgA).
Saliva contains an epidermal growth factor (EGF).
Saliva contains nerve growth factor (NGF).
Taste, smell, and nerve endings in the periodontal ligament and muscles of mastication play a role in saliva secretion.
Salivary secretion depends on gustatory and masticatory stimulation.
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Salivary Duct Systems
The duct system consists of a secretory portion, which lies among the acinar cells, and an excretory portion, which lies in the connective tissue septa between the lobules and lobes of the glands. These ducts continue beyond the glands, emptying into the oral cavity.
The secretory portion allows substances to enter and leave the cells by ion exchange with adjacent blood vessels. The excretory duct is a saliva-collecting tube.
Acinar cells drain directly into intercalated ducts, which opens directly into a larger duct, called the striated duct. Cells of the striated duct allow for sodium resorption and potassium secretion.
Both intercalated and striated ducts are part of the intralobular duct system, located inside the lobules. The remaining interlobular excretory ducts are located in the connective tissue septa, between the lobules and lobes of the gland.
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Salivary Duct Systems
Stensen duct drains the parotid gland.
Wharton duct drains the submandibular gland.
The Stensen duct drains the parotid gland.
The Wharton duct drains the submandibular gland.
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22. Innervation of the Salivary Glands
Salivary gland secretion is regulated mostly by the postganglionic sympathetic and parasympathetic autonomic nervous systems, with cell bodies located within specific ganglia of the head and neck.
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Myoepithelial Cells
Myoepithelial cells originate from the oral epithelium when the oral epithelial cells of the salivary gland grow into the mesenchyme. The cells function as muscle cells to contract and squeeze the acinus, facilitating secretion.
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24. Classification of Tonsillar Tissue
Waldeyer ring
Pharyngeal tonsil or adenoid
Palatine tonsils
Lingual tonsils
Tonsils are part of the lymphatic system, which also includes lymph nodes, thymus, spleen, and diffuse lymphatic tissue.
The lymphatic nodules may have germinal centers, which are active sites of lymphocyte formation. These centers are common in the lingual and palatine tonsils.
The pharyngeal tonsil is covered with respiratory epithelium. The palatine and lingual tonsils are covered with stratified squamous epithelium.
Tonsils and lymph nodes have efferent lymphatic vessels draining them.
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Palatine Tonsils
Infected and swollen palatine tonsils appear red, with streaks of white purulent material on their surfaces. Bacteria lodges in the deep, branching crypts. These crypts may become plugged with lymphocyte discharge and desquamated epithelial cells. Beneath the palatine tonsils are seromucous glands, which assist in flushing out these crypts.
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Palatine Tonsils
Each lobule contains lymphatic nodules, which contain germinal centers. Septa of connective tissue support the nodules of lymphatic tissue and invest the gland in a capsule.
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Lingual Tonsils
Lingual tonsils are bilateral masses, located on the surface of the posterior third of the tongue. The tonsils are composed of wide-mouthed crypts and are nonbranching. They form rows of lymphatic nodules supported by connective tissue septa that are present in each lobule of the gland.
They are surrounded by a connective tissue capsule, which is covered by nonkeratinized, stratified, squamous epithelium.
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Pharyngeal Tonsil
The pharyngeal tonsil or adenoid is located in the posterior wall of the superior portion of the nasopharynx.
If the pharyngeal tonsil grows laterally from the midline to surround the opening of the eustachian tubes, it can be the source of infection to the eustachian tubes.
The pharyngeal tonsil does not have an aggregation of lymphocytes with crypts, but it does have occasional folds that appear as clefts in the mucosa.
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Functions of Tonsils
They produce lymphocytes.
Some lymphocytes transform into T cells and engulf bacteria or discharge substances to destroy them.
Other lymphocytes transform into B cells, which differentiate into plasma cells .
Some foreign substances are absorbed from the gland crypts into the gland proper and are then destroyed.
Lymphocytes protect the body from foreign microorganisms inhaled or swallowed. Lymphocytes have been called memory cells.
Plasma cells secrete antibodies that destroy antigens.
Plasma cells and lymphocytes are found in chronic infections, such as periodontal disease.
Plasma cells in the area of salivary glands produce IgA, which joins in the end piece of the intercellular area to form secretory IgA.
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30. Questions and Considerations
Considering saliva function, what are some good patient education points?
Discuss drugs and medications that can contribute to decrease salivary flow.
Why is salivary flow important to older patients?
How should the dental professional respond to the mother’s question about having her child’s tonsils removed?
Check for student understanding.
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