Histology of Salivary Glands 2024 (1).pdf

15.02.2024 Histology of Salivary Glands Yasemin Ersoy Çanıllıoğlu Learning Objectives Classify the salivary glands Describe the general histological features of the exocrine gland and in relation to this, major and minor salivary glands Identify parotid, submandibular and sublingual salivary glands...

15.02.2024 Histology of Salivary Glands Yasemin Ersoy Çanıllıoğlu Learning Objectives Classify the salivary glands Describe the general histological features of the exocrine gland and in relation to this, major and minor salivary glands Identify parotid, submandibular and sublingual salivary glands on the basis of histological appearance and by the types of secretion produced by each gland. Identify excretory ducts of the salivary gland and correlate the structural features of the constituent cells to the functions of these ducts. Describe the stroma of the salivary glands with their cells such as myoepithelial cells and nerves in relation to the acinar cells, and their role in secretory functions 1 15.02.2024 What is the gland Gland is an organ of secretion made up of specialized secretory cells derived from the surface epithelium 2 15.02.2024 General Features Epithelial in origin Present as discrete organs or in layers. Secretory cells form functional units called secretory end pieces Excretory duct Fluid secreted may be enzymes, hormones or mucus. Secretion is modulated by nervous and hormonal influences. Classification of exocrine glands structure of the secretory units tubular alveolar (acinar). structure of the excretory duct, simple (unbranched duct) branched or compound (branched duct) secretory product, serous - secrete a watery fluid mucous - secretion is thick and rich in glycoproteins. 3 15.02.2024 Digestive Glands The three major digestive glands Salivary glands The exocrine pancreas secretes a combined aqueous and enzymatic product draining into the duodenum. The liver, a combined endocrine and exocrine gland Products of these organs facilitate transport and digestion of food within the gastrointestinal tract. Salivary Glands The main functions of the salivary glands are to moisten and lubricate ingested food and the oral mucosa, to initiate the digestion of carbohydrates and lipids with amylase and lipase, to secrete innate immune components such as lysozyme and lactoferrin. 4 15.02.2024 Salivary Glands The Major Salivary Glands External to mouth and duct to mouth Secrete saliva only right before or during eating There are three bilateral pairs of major salivary glands, the parotid, submandibular, and sublingual glands (branched tubuloalveolar glands ), which together produce about 90% of saliva. The Minor Salivary Glands  located throughout the oral mucosa and tongue  secrete saliva all the time to keep mouth moist  lingual, labial, buccal, molar and palatine glands General Organization of the Gland  The glands are surrounded by a connective tissue capsule from which trabeculae/septae extend into the parenchyma and divide the organ into lobes and lobules. 5 15.02.2024 Stroma and Parenchyma The secretory units and their ducts which originate from the surface epithelium are the parenchyma of the gland Connective tissue that supports the parenchyma of the gland is called stroma – Capsule – Septa (interlobular, interlobar) – Loose intralobular connective tissue supporting the parenchyma Parenchyma of the gland The major salivary glands a secretory portion (asinus) a duct portion (intralobular, interlobular, main excretory duct) 6 15.02.2024 The secretory portions/ alveolar or tubules Serous cells Mucous cells Myoepithelial cells The secretion of each gland is either serous, seromucous, or mucous, depending on its content of the glycoprotein mucin. 7 15.02.2024 The secretory portions - Serous cells/Serous Acini pyramids shaped have single, round, basally located nuclei, RER and Golgi complex abundant apically secretory granules serous cells form a spherical unit called an acinus (L. grape), with a very small central lumen. There are complex foldings of cytoplasmic membrane they secrete proteins, lactoferrin, and enzymes (amylases, peroxidases, lysozyme) tight junctions with each other. apical to the tight junctions, intercellular canaliculi communicate with the lumen. 8 15.02.2024 Serous Acini The secretory portions - Mucous cells flattened nucleus and basally located Production, storage, and secretion of proteinaceous material; smaller enzymatic component -more carbohydrates-->mucins The apical region of the cytoplasm is occupied by secretory granules less intercellular canaliculi Mucinogen granules are PAS positive they are water soluble and lost during routine tissue preparations. For this reason the cytoplasm of mucous cells appear empty in H&E stained paraffin sections Mucous cells are most often organized as cylindrical tubules rather than acini. Goblet cells 9 15.02.2024 10 15.02.2024 Mucous Acini Mixed Acini Contain both mucous and serous acini- mixed tubuloacinar secretory units also occur short mucous tubules with distal clusters of serous cells called ‘’serous demilunes’’ 11 15.02.2024 12 15.02.2024 The secretory portions - Myoepithelial Cells Share the same basal lamina with acinar cells Wrap around the acini and ducts The myoepithelial cells of the intercalated ducts are more spindled-shaped and fewer processes They similar to smooth muscle cells Their contractions assist in expelling the secretion from the acini Support secretory cells Contract and widen the diameter of the intercalated ducts 13 15.02.2024 Duct portion of the gland Intralobular (secretory) duct – Intercalated duct (neck portion) – Striated duct – Excretory intralobular duct Interlobular(excretory)duct Interlobar duct Main (excretory) duct 14 15.02.2024 Duct portion - Intercalated Duct Lined by squamous-low cuboidal cells Myoepithelial cells are also present Most prominent in serous secreting salivary glands In mucous secreting salivary glands, it is short and difficult to identify Intercalated duct Duct portion - Striated Duct Lined by simple cuboidal to low columnar epithelium Striated ducts have distinguishing basal striations due to membrane invagination and mitochondria Reabsorbtion of sodium from the primary secretion Secretion of potassium and bicarbonate into the secretion Modify the secretion – Hypotonic solution= low sodium, chloride and high potassium 15 15.02.2024 16 15.02.2024 The acinus, intercalated duct, and striated duct – a single secretory unit called a salivon Duct portion - Excretory Intralobular Ducts initially lined by cuboidalto-columnar epithelium located in the lobule as they grow in size, the CT surrounding gets thicker 17 15.02.2024 Duct portion - Interlobular Ducts located outside the lobule, between adjacent lobules. lined by pseudostratified columnar epithelium Duct portion - interlobar ducts and main duct interlobar duct is lined by stratified columnar epithelium main duct is lined by stratified columnar epithelium or stratified squamous epithelium at the end its – near the opening into the oral cavity. 18 15.02.2024 19 15.02.2024 20 15.02.2024 Salivary glands secrete the SALIVA Saliva Hypotonic solutions of 99.5% water 1000ml – 1200 ml/day pH of 6.8 to 7.0 Parasympathetic system induces secretion of waterrich saliva Sympathetic system induces secretion of protein-rich saliva Content – Amylase, lingual lipase, lysozyme, IgA, electrolytes 21 15.02.2024 Saliva Functions Lubrication – Mucus and water Dissolve food for the function of the taste buds Moisten food for easy swallowing Protection - antibacterial function – – – – Lysozyme - attacks the walls of bacteria, kills bacteria Lactoferrin - chelates iron necessary for bacterial growth IgA - inhibits bacterial growth forms a protective film on the teeth called pellicles Digestion – Amylase – begins the digestion of carbohydrates – Lingual lipase – digests fat – provides calcium ad phosphate essential for teeth development and maintenance Formation and Secretion of Saliva Primary saliva – Serous and mucous cells, intercalated ducts – Isotonic Modified saliva – Striated duct – remove Na+ and Cl- and secrete K+ and HCO3– End product is hypotonic 22 15.02.2024 Major Salivary Glands/ Parotid Gland  Largest of the major salivary glands  A pair of glands  Opens to the oral cavity through the Stensen’s Duct (Stenon duct)(Second superior molar)  Completely- pure serous gland  Contains adipose cells  Intercalated duct - longest in Parotid gland  Opens to the oral cavity through the Stensen’s Duct (Stenon duct)(Second superior molar) Parotid Gland Vein Serous acini Interlobular Excretory duct Fat cells Arteriol Intercalated duct Interlobular Excretory duct Striated ducts Intercalated duct Serous acini Interlobular connective tissue septa Interlobular Excretory duct Myoepithelial cells Serous acinus Intercalated duct Striated duct Interlobular Excretory duct 23 15.02.2024 Parotid Gland Parotid Gland 24 15.02.2024 Parotid Gland Parotid Gland - Clinical significance Mumps, rabies, and tumors The parotid gland is the primary target of the rabies and mumps virus transmitted in saliva containing the virus. Two complications of mumps are orchitis and meningitis. – Bilateral orchitis caused by the mumps virus can result in sterility. The most common site of tumors, malignant or benign 80% of salivary gland cancers are in the parotid gland 25 15.02.2024 Major Salivary Glands/ Submandibular Gland:       Smaller A pair of glands Sero-mucous (mixed) gland Serous component is predominant. Serous Demilunes Opens to the oral cavity through the Wharton’s Duct (base of tongue) Submandibular Gland Arteriol Fat cells Vein Serous demilune Mucous acinus Interlobular connective tissue septa Intercalated duct Striated ducts Mucous acinus Intercalated duct Mucous acini Striated duct Serous acini Interlobular Excretory duct Serous demilune Intercalated duct Myoepithelial cells Basal infoldings Serous acinus Mucous acinus Intercalated duct Striated duct Well developed in the submandibular gland – striated duct 26 15.02.2024 Submandibular Gland Submandibular Gland 27 15.02.2024 Submandibular Gland Major Salivary Glands/ Sublingual Gland:        Small salivary glands located underneath the tongue A pair of glands Sero-mucous (mixed) gland Mucous component is predominant Serous Demilunes Opens to the oral cavity through the Major Sublingual Duct (Duct of Rivinus) or Wharton’s duct Most of them open directly into the floor of mouth 28 15.02.2024 Sublingual Gland Intralobular Excretory duct Serous demilune Mucous acini Intercalated duct Fat cells Arteriol Serous acini Interlobular connective tissue septa Vein Interlobular Excretory duct Striaed duct Serous acinus Myoepithelial cells Mucous acinus Mucous acinus w/ serous demilune Intercalated duct Interlobular Excretory duct Sublingual Gland Serous demilune Mucous acini Intercalated duct Mucous acini Striated duct Serous acini 29 15.02.2024 Sublingual Gland Serous Demilunes- Gianuzzi’s Demilunes 30 15.02.2024 Submandibular Gland Sublingual Gland Parotid Gland A person will create enough saliva to fill two average size swimming pools during her/his lifetime 31