Salivary Glands Lecture 2024 - Case Western Reserve University PDF

Case Western Reserve University School of Dental Medicine Salivary Glands Karla Coburn, Ph.D. [email protected] Learning Objectives 1. Describe the general classification of salivary glands 2. Describe the general structure of a salivary gland and the differences between pa...

Case Western Reserve University School of Dental Medicine Salivary Glands Karla Coburn, Ph.D. [email protected] Learning Objectives 1. Describe the general classification of salivary glands 2. Describe the general structure of a salivary gland and the differences between parenchyma and stroma. 3. Compare and contrast the different cells of the secretory units: serous vs mucous cells 4. Compare and contrast the different types of ducts of the duct system. 5. Identify main components and functions of saliva 6. Describe the key histologic features of the major salivary glands: parotid, submandibular and sublingual glands. 7. Describe the structure and function of the minor salivary glands. 8. Identify clinical correlations associated with the salivary glands. Mescher, A. Junqueira's Basic Histology: Text and Atlas. New York: Lange, McGraw Hill, 2018 15th ed. Chapter 16: Digestive Tract and Organs Associated with Digestive Tract- Section on Salivary Glands Connect to this resource at AccessMedicine (CWRU Only) or http://accessmedicine.mhmedical.com/book.aspx?bookid=2430 Components of the GI System The digestive tract consists of: Oral cavity Pharynx Esophagus Stomach Small and large intestine Anus Organs associated with the digestive tract: Tongue, Teeth Salivary glands Pancreas Liver Gallbladder Class Outline 1. General classification and structure of exocrine Glands 2. General structure of salivary glands 3. Saliva: composition and functions 4. Major Salivary Glands 5. Minor Salivary Glands 6. Control of Salivation 7. Clinical Correlations Salivary glands: Classification ✓ Salivary glands are exocrine glands that can be classified as: ✓ Compound glands: branching ducts Merocrine glands Salivary glands can be and multiple secretory units: tubular, secretion is released by further categorized as acinar, or tubuloacinar secretory portions. exocytosis either serous or mucous Class Outline 1. General classification and structure of exocrine glands 2. General structure of salivary glands 3. Saliva: composition and functions 4. Major Salivary Glands 5. Minor Salivary Glands 6. Control of Salivation 7. Clinical Correlations  Salivary glands: Stroma vs Parenchyma ✓ Parenchyma: it is the functional tissue of the gland; capsule includes secretory units and ducts. ✓ Stroma: all the connective tissue (CT) associated with the parenchyma. Includes the capsule, the septa that subdivide the gland into lobules and all the loose CT between the secretory units. septa ✓ The stroma components provide support and allow the lobule distribution of nerves and blood vessels throughout the gland. ✓ Plasma cells within the CT release IgA into the salivary secretion Salivary glands: Stroma vs Parenchyma capsule https://histologyguide.com/slideview/MH-095-submandibular-gland/12-slide-1.html?x=8341&y=15029&z=59.0 Septum Nerves Blood vessels septa Excretory duct lobule Secretory units Parenchyma: Secretory Units Frequently surrounded by myoepithelial cells Serous demilune Serous acini (spherical) Mucous tubules (tubular) Mixed Mixed Units: seromucous Serous demilunes or half-moons: caps of serous cells associated to a mucous tubule Serous demilune mucous tubule Conventional Fixation Rapid Freezing Parenchyma: secretory units and cells Serous cells ✓ Pyramidal shape, large rounded nucleus, abundant rough ER, Golgi and secretory zymogen granules. ✓ Normally arranged in acini or serous demilune. Serous cell Mucous cell Mucous cells ✓ Flattened basal nuclei. RER/Golgi produce heavily glycosylated proteins called mucins. Foamy aspect. ✓ When mucins are released from the cell, they become hydrated and form a layer of mucus. ✓ Normally arranged in tubules Serous vs. Mucous cells Serous Mucous Secretion Thin, watery Thick, viscous Proteinaceous secretion but poorly Proteinaceous secretion highly glycosylated glycosylated Granules Eosinophilic granules containing enzymes Mucinogen granules (or proenzymes) Nucleus Central rounded nucleus Flattened basal nuclei Type of secretory Acini: round units with small lumen Tubules: tubular units with larger lumen unit they form Cell boundaries Indistinct Distinct HE stain Darkly stained Lightly stained (look pale) Function Enzymatic action Protection & lubrication Examples Parotid, Pancreas Sublingual gland, goblet cell Myoepithelial cells ✓ Spindle-shaped cells found in glandular epithelial and found between basal membrane and secretory cells ✓ Embrace gland acini like an “octopus on a rock” ✓ Contain actin: contract and squeeze out secretory product Parenchyma Myoepithelial cells Intercellular secretory canaliculi Myoepithelial cells Secretory units - Serous acini (spherical) - Mucous tubules (tubular) - Mixed Serous acinus Frequently surrounded by Serous demilune Intercalated myoepithelial cells duct of a mixed secretory unit Intercalated ducts Duct system - Intercalated Intralobular - Striated - Excretory Extralobular (within the CT septae) Striated ducts Basal laminae Mucous tubule Intralobular Ducts: Intercalated and Striated ducts ✓ Secretory acini and tubules empty into intercalated ducts, lined by cuboidal epithelial cells, and several of these ducts join to form a striated duct (columnar cells, eosinophilic, membrane folds) Intercalated duct cell Striated duct cell Duct System Striated duct Intralobular ducts Primary secretion Myoepithelial cell Acinus Product of the secretory units Intercalated duct Secondary secretion K+ Ionic modification of the Na+ primary secretion, Striated performed by striated Cl- duct ducts. HCO3- Saliva: slightly hypotonic and rich in bicarbonate Excretory ions duct Buffering capacity Oral epithelium Fascicle 9 Chapter 1 (1).pdf  https://histologyguide.com/slideview/MH-096-sublingual-gland/12-slide-1.html?x=17765&y=9231&z=66.6 ✓ From pseudostratified epithelium to stratified squamous epithelium (oral epithelium) Sublingual Gland https://histologyguide.com/slideview/MH-094hr-parotid/12-slide-1.html?x=1496&y=14833&z=29.8 Parotid Gland Duct System: Extralobular ducts Components of Salivary Glands Serous acini secretory units Mucous tubules intercalated duct striated duct excretory duct parotid submandibular sublingual Class Outline 1. General classification and structure of exocrine glands 2. General structure of salivary glands 3. Saliva: composition and functions 4. Major Salivary Glands 5. Minor Salivary Glands 6. Control of Salivation 7. Clinical Correlations Composition of Saliva What is saliva and ✓ Mostly water (97–99.5%) what role does it play in oral health? ✓ Slightly acidic (pH 6.75 to 7.00) ✓ Electrolytes: Na+, K+, Cl−, Ca2+, PO42−, HCO3− ✓ Digestive enzymes: α-amylase and lipase ✓ Lysozyme, IgA, defensins, mucinogens ✓ Metabolic wastes: urea and uric acid ✓ In addition to the secretion from the major and minor salivary glands, whole-mouth saliva contains components of non–salivary gland origin: discarded oral epithelial cells food debris bacteria and other microorganisms, gingival crevicular fluid mucosal transudate Functions of Salivary Glands 1) Moisten and lubricate ingested food and the oral mucosa, facilitating chewing, bolus formation, swallowing and articulation of speech 2) Initial digestion of carbohydrates/lipids: amylase and lipase 3) Cleanses mouth and dissolves food chemicals for taste 4) Formation of the acquired dental pellicle, a thin coating layer covering all solid surfaces in the oral cavity. 5) Tissue repair and enamel remineralization 6) Antimicrobial activity 7) IgA secretion 8) pH maintenance: tooth integrity and allows amylase activity Class Outline 1. General classification and structure of exocrine glands 2. General structure of salivary glands 3. Saliva: composition and functions 4. Major Salivary Glands 5. Minor Salivary Glands 6. Control of Salivation 7. Clinical Correlations Salivary Glands Major salivary glands: Stensen's duct Parotid, submandibular, sublingual Minor Salivary Glands ✓ Scattered throughout submucosa of oropharynx and oral cavity Wharton's duct Parotid Gland: Stensen’s duct Stensen's duct Parotid gland ✓Make 25% of volume of saliva ✓Well defined capsule, consists mostly entirely of serous acini ✓Long and numerous intercalated ducts, numerous striated ducts Striated ducts ✓Secretion: serous and watery, with α-amylase and Intercalated ducts proline-rich proteins Parotid gland Intercalated ducts Serous acini Plasma cells Adipocytes Parotid gland Striated duct Plasma cell Mast cell Serous acini Intercalated duct Parotid gland Striated ducts Intercalated duct Submandibular gland ✓ Mixed gland (seromucous), mostly serous: serous acini and serous demilunes ✓ Make 60% of volume of saliva ✓ Make salivary epidermal growth factor (EGF) ✓ Mucous units make mucus for moisture and lubrication. ✓ Serous cells secrete: α-amylase Proline-rich proteins Lysozyme (hydrolysis of bacterial walls) Wharton’s duct: sublingual caruncle Wharton's duct Wharton’s duct Frenulum of tongue Sublingual Sublingual gland folds Sublingual caruncle Sublingual caruncle Netter Wharton’s duct: sublingual caruncle LP Motor neurons within submandibular ganglion MP MP Submandibular gland Submandibular MH ganglion Sobotta, 2006. Netter  Submandibular Intercalated ducts Submandibular Gland ganglion Serous acinus Mixed unit Nerves connective Blood tissue septae vessel Extralobular Striated duct ducts https://histologyguide.com/slideview/MH-095-submandibular-gland/12-slide-1.html?x=8341&y=15029&z=59.0  Submandibular Gland Serous demilunes Striated ducts mucous cells https://histologyguide.com/slideview/MH-095-submandibular-gland/12-slide-1.html?x=8341&y=15029&z=59.0 serous demilunes mucous cells Intercalated ducts connective tissue septae Striated ducts https://histologyguide.com/slideview/MH-095-submandibular-gland/12-slide-1.html?x=8341&y=15029&z=59.0 ducts Intercalated acini tubule Serous mucous Submandibular Gland ducts Striated Submandibular Gland Plasma cells Mucous tubule Serous demilunes Striated ducts Serous acini Intercalated ducts https://www.pathologyoutlines.com/topic/salivaryglandsnormalhistology.html  Sublingual gland ✓ Bilateral, paired, with much shorter ducts. ✓ Produce a predominantly mucous product and only about 3-5% of salivary volume Frenulum ✓ Mixed gland, but mostly mucous of tongue (70%) gland, hence the poor staining. Sublingual ✓ Several small excretory ducts open folds on the sublingual folds. If only one is present: Bartholin duct Sublingual Sublingual gland caruncle Netter Sublingual Gland Main excretory duct mucous tubules Extralobular ducts  mucous tubules Sublingual Gland Intercalated duct Serous demilune serous demilune Sublingual Gland mucous tubule (H&E, 600×) Sublingual gland, mucinous acini Joaquín J. García. Atlas of Salivary Gland Pathology. 2019 serous demilunes  Serous Sublingual Gland demilune Intercalated duct Striated ducts Serous acinus Sublingual Gland Extralobular duct: Striated ducts: pseudostratified columnar epithelium simple columnar epithelium Intercalated duct: simple cuboidal epithelium Intercalated duct Class Outline 1. General classification and structure of exocrine glands 2. General structure of salivary glands 3. Saliva: composition and functions 4. Major Salivary Glands 5. Minor Salivary Glands 6. Control of Salivation 7. Clinical Correlations Minor Salivary Glands ✓Small volume (~10%) but continuous secretion: coat the oral cavity with saliva. ✓Secretion: overall mucous (70% of all salivary mucins), with significant quantities of IgA and antibacterial proteins. Crucial role in the protective mechanisms of oral mucosa and enamel surface Features: ✓ Not encapsulated by connective tissue ✓ Less developed duct system. ✓ Scattered throughout submucosa of oral cavity/oropharynx: hard/soft palate,uvula tonsillar pillars, tongue, lips, buccal mucosa. ✓ Continuous secretion Lips Labial salivary glands Tongue The minor salivary glands in the tongue are in intimate contact with the striated muscle https://histologyguide.com/slideview/MHS-264-tongue/14-slide-1.html?x=21756&y=9073&z=25.0 Von Ebner’s Glands ✓ Von Ebner’s glands are a special group of salivary glands (serous type) found at the base of the circumvallate papillae ✓ Provides a continuous flow of fluid over the taste buds lining the sides of the papillae. This flow is important for dissolving the food particles to be tasted and flush away residual particles. They aid in the perception of taste and digestion through secretion of digestive enzymes and proteins Von Ebner’s Glands Von Ebner’s ducts Von Ebner’s glands Buccal mucosa  Palate rugae Palatine raphe Soft palate Hard palate Class Outline 1. General classification and structure of exocrine glands 2. General structure of salivary glands 3. Saliva: composition and functions 4. Major Salivary Glands 5. Minor Salivary Glands 6. Control of Salivation 7. Clinical Correlations What makes your mouth water? Control of Salivation ✓ Up to 1500 ml/day can be produced. ✓ Action of Parasympathetic and Sympathetic Parasympathetic stimulation ✓ Minor salivary glands: basal production (enough to keep mucosa moist) ✓ Major salivary glands: copious watery secretion with little organic content activated by: ✓Smell/sight of food ✓ Ingested food: stimulates chemoreceptors and mechanoreceptors in mouth ✓ Signals are received by Salivatory nuclei in brain stem that stimulate parasympathetic impulses along fibers in cranial nerves VII (to submandibular and sublingual) and IX (to parotid glands). Sympathetic stimulation ✓ Causes myoepithelial cells contraction and exocytosis of serous granules (α-amylase) ✓ Strong sympathetic stimulation inhibits salivation and results in dry mouth (xerostomia) Class Outline 1. General classification and structure of exocrine glands 2. General structure of salivary glands 3. Saliva: composition and functions 4. Major Salivary Glands 5. Minor Salivary Glands 6. Control of Salivation 7. Clinical Correlations Salivary Glands and Aging ✓Aging salivary glands show some structural changes:  Decrease in acinar tissue of major glands  Increase in fibrous and fatty tissues  Decrease in minor salivary gland number ✓Changes in saliva content:  Decrease in the volume of mucin  Decrease in concentration of IgA Sialolithiasis Stone formation (crystallized minerals) in ducts  Common in submandibular and parotid  Painful, swelling due to blockage, can abscess if not treated Chronic submandibular sialadenitis with sialolithiasis. A sialolith obstructs the dilated lumen of an Removal of 3-cm giant sialolith from the submandibular Wharton’s duct of a 4-year-old child. interlobular duct and contains many lamellae and several central cores. Bar = 100 μm https://entokey.com/11-pediatric-endoscopic-salivary-gland-surgery/ Mucoceles ✓ Mucoceles most often involve the minor salivary glands of the lower lip, buccal mucosa, and floor of the mouth. ✓ They are thought to result from ductal obstruction or trauma and represent accumulation and extravasation of mucus into adjacent tissues. Mucocele Ranula: mucocele from the sublingual gland Saliva as a potential source of virus/bacteria spread Saliva is a body fluid with multiple biological functions which not only protects humans from harmful agents, but also acts as a potential route for the spread of diseases. ✓ Coronavirus ✓ Rhinovirus (colds) ✓ Flu virus ✓ Epstein-Barr virus (mononucleosis) ✓ Type 1 herpes (cold sores) ✓ Strep bacteria ✓ Hepatitis B and hepatitis C ✓ Paramyxovirus (Mumps) virus ✓ Cytomegalovirus (a risk for babies in the womb) Xerostomia: Hyposalivation ✓ Head and neck radiation ✓ Sjogren Syndrome ✓ Drug-related Signals and symptoms: ✓ Halitosis ✓ Rampant cavities Oral lesions ✓ Oral mucosa lesions: cracked lips, tongue ✓ Burning sensation ✓ Opportunistic infections ✓ Dysphagia Candidiasis ✓ Lymphocytic infiltrate Caries