Salivary glands intro to teeth Jan Krivanek 1. 3. 2023 Lecture 2 • Overview of the salivary glands of the oral cavity and their microscopic structure • Large salivary glands - topography, structure and description. • Saliva • TMJ Salivary glands - glandulae salivariae Exocrine glands with watery, mucous or mixed secretions Formed by proliferation of the ectoderm of the primitive oral cavity into the ectomesenchyme (composite organ) Salivary glands classification • According to the type of secretory compartments and the nature of the secretion: serous - acini mucinous - tubules mixed - acini, tubules + tubules with Gianuzzi lunules (tubuloacinary units) • According to size: large – gl. parotis, gl. submandibularis a gl. sublingualis small – in tela submucosa, the number of 800 - 1000 General structure of large salivary glands • Ligament capsula fibrosa septa (+ vessels, nerves, interlobular and larger ducts) • Parenchyma lobes Glandular compartments (serous acini, mucinous tubules, serous lunules) Ducts (intercalated, striated, interlobular, main) Ligament gl. parotis and gl. submandibularis ligament forms capsule gl. sublingualis and gl. lingualis anterior capsule incomplete septae Glandular tissue (parenchyma) The lobules contain: secretory compartments: serous acins, mucinous tubules or tubules with Gianuzzi lunules + 2 parts of the duct system - intercalated and striated ducts (interlobular and main - in septal ligament) Structural components of the salivary glands Wall of secretory compartments: - basement membrane - myoepithelial cells - glandular cells Wall of intercalated and striated ducts - basement membrane - myoepithelial cells (interalated ducts only) - Epithelial cells tubules Secretory compartments Serous aciniMucinous tubules Tubules with lunules Serous acini spherical to ovoid sacs (60 - 150 µm) with a narrow lumen wall: serous cells, myoepithelial cells, basement membrane Cells • pyramidal shape and spherical nucleus at the base • below the nucleus is a basophilic cytoplasm (rER, mitochondria and ribosomes) • supranuclear - eosinophilic secretory grains / zymogenic = proenzyme (zymogen = inactive enzyme precursor) Serózní buňky Watery secretion, rich in proteins and enzymes Serous cells Serous acini Rat salivary gland parenchyma: SA – serous acinus, SG – secretory granule, K – capillary. TEM, primary magnification 1,500x Mucinous tubules Usually larger diameter than serous acins (about 200 μm), distinct lumen On sections: transversely or longitudinally sectioned Wall: cylindrical mucinous cells, myopithelial cells and basement membrane Flattened nuclei Apexes - numerous grains of mucinogen Viscous mucus secretion Tubules with lunules (Gianuzzi) - tubuloacinary units Lunule (demilune) = aggregation of serous cells at one or both ends of a mucinous tube, similar to a demilunes Secretory compartments Serous aciniMucinous tubules Tubules with lunules • Serous acini • Mucinous tubules • Lunules (demilunes) Secretory compartments Myoepithelial cells Capable contractions, Vegetative control They regulate secretion, control nutrient supply and control electrolytes Inserted between the bases of secretory cells (acins and tubules) and the basement membrane Flattened body, several protrusions, between secretory and myoepithelial cells numerous desmosomes or hemidesmosomes In the cytoplasm actin microfilaments (bundles) + cytokeratin filaments The cells help to release the secretion into the lumen of the secretory compartments and its further passaged through the inserted ducts (in the wall of which they are also present) Active from the 25th week of development Salivary ducts types – Intercelular (they do not have their own wall, intercellular space) – Intercalated (simple squamous ep., only serous and mixed glands) – Striated (simple cuboidal/low columnar ep.; basal labyrinth➔ striation) – Interlobular (simple – stratified columnar ep., in septs) – Main (stratified columnar ep.) Ducts Intercalated StriatedIntercellular Main Interlobular Intercalated ducts Narrow and thin-walled channel, collapsed on slides Wall: basal membrame, myoepithelial cells and simple squamouse to low cubic ep. Numerous in serous type of glands (cells of intercalated ducts secrete to saliva macromolecular substances: lysozym + lactoferin) Striated ducts Wider than the intercalated ducts (easy to find), usually in the middle of lobe Wall: Basal membrane and simple cuboidal/low columnar ep. Microvilli on apexes and an bases characteristic striation (basolateral labyrinth) In the cytoplasm of cytokeratin filaments Glandula submandibularis The cells of striated ducts regulate the content of water and electrolytes (Na+, K+, Cl-, Ca2+, Mg2+, HCO3-) in the secretion. Resorption of Na+, and ClSecretion of K+ and HCO3nerve control Striated duct – basal labyrinth Base of epithelial cell: Invagintion of cytoplasmic membrane, numerous mitochondria Epithelial cell Interlobular and main ducts Interlobular ducts Located in fibrous septae between the lobes (columnar or stratified columnar epithelium) They are formed by the connection of several striated ducts Lined by a high single-layer columnar and in the terminal sections also a stratified columnar epithelium Main ducts Stratified columnar ep. with goblet cells Ductus parotideus Ductus submandibularis Ductus sublinguales (major et minores) Main ducts Stratified columnar ep. In epithelium Goblet cells Wall supported by the dense collagenous connective tissue and smooth muscle cells Ductus Rivini (V) – septum of gl. sublingualis. Topography od large salivary glands Ductus parotideus Ductus submandibularis Ductus sublinguales (major et minores) Glandula parotis • SEROUS gland • 14 - 28 g • capsule, septs and lobules • Serous acini, ducts: long intercalated ducts, numerous of striated ducts • ductus parotideus (Stenoni) - 2. upper molar (Steno/Stensen, Niels) • adipocytes Papilla parotidea Glandulaparotis Glandula submandibularis • MIXED tuboalveolar gland, predominantly SEROUS • 10-15 g • serous acini - 80 %, rest are mucinous tubules with Gianuzzi demilunes • intercalated and striated ducts • ductus submandibularis (Whartoni) - frenulum linguae trigonum submandibulare Glandula submandibularis Glandula sublingualis • MIXED tuboalveolar gland, predominantly MUCOUS • 2g • located on the floor of the mouth on mylohyoid muscle near the midline • Mucinous tubules, serous acini are rare, instead of them: Gianuzzi demilunes • Intercalated ducts are missing, striated ducta are present, but are reduced in number and short • ductus sublingualis major (Bartholini) • ductus sublinguales minores (Rivini) along the crest of the plica sublingualis Glandula sublingualis Saliva Product of all salivary glands of the oral cavity 1.0-1.5 liters / day (0.3-0.6 ml / min) Small glands 10 % / large glands 90 % (gl. Parotis 25 %, gl. Submand. 60-65 %, gl. Sublingualis 10 %) Clear or slightly opalescent viscous liquid, slightly acidic pH: 6.8 (6.5 - 7.2) It consists of a liquid and solid component: Liquid: water (95 %) ions - Na +, K +, Cl-, Ca2 +, Mg2 +, HCO3-, etc. proteins: amylase (ptyalin) and maltase, peroxidase, lysozyme, lactoferrin glycoproteins - mucus (mucin) immunoglobulins (Ig A, IgG and IgM) small organic molecules (glucose, amino acids, urea, uric acid, etc.) Formed: removed dead cells of the epithelium of the oral cavity, salivary bodies (altered lymphocytes) and non-pathogenic saprophytic bacteria 2 stages of saliva production: primary saliva (isotonic) – before passing through striated ducts and definitive saliva (hypotonic) - was modified by striated ducts Saliva function Protective: forms a thin film on the surface of the mucosa and teeth - a salivary film stimulates repair processes in the oral cavity participates in remineralization and maintains tooth integrity ensures moisture and self-cleaning of the oral mucosa protects teeth from bacteria Antimicrobial: proteins with bacteriostatic effect - lysozyme, peroxidase, lactoferrin, etc. Moisturizing: moisturizes dry food and makes them easier to swallow Digestive: initiates cleavage of polysaccharides (salivary amylase) saliva is a sensitive indicator of oral health (changes during periodontal disease, caries, candidiasis, etc.) Location Name Type Size Lips gll. labiales sup. et inf. mixed, pred. mucinous minor Cheeks gll. buccales mixed, pred. mucinous minor gll. molares (retromolares) mixed, pred. mucinous minor GL. PAROTIS serous MAJOR Palate hard gll. palatinae (glandular zone) mucinous minor soft gll. palatinae mucinous minor Tongue Apex gl. apicis lingue (Blandini-Nuhni) mixed, pred. mucinous minor/ major Terminal sulcus gll. Ebner‘s (gll. papillae vallatae) serous minor Base gll. Weber‘s (gll. linguales post.) mucinous minor Floor of the mouth GL. SUBMANDIBULARIS mixed, pred. serous MAJOR GL. SUBLINGUALIS mixed, pred. mucinous MAJOR Pathology (diseases) of the salivary glands Sialadenitis (sialoadenitis) – inflammation of the salivary glands, of bacterial or viral origin Sialolithiasis - saliva in the ducts becomes a viscous to such an extent that the concentrated secretion can secondary calcify - prevents drainage - impermeability of the outlets Sialolithiasis in small salivary glands - dilatation of secretory compartments (mucocele), and enlargement of glands In case of obstruction of the ductus submandibularis - large retention cyst located at the base of the oral cavity - ranula Control of salivary gland function Autonomic nervous system: efferent fibers enter the glands from the parasympathetic and thoracic sympathetic fibers, forming dense network on the surface of the secretory compartments and ducts Stimulation of sympathetic fibers reduces saliva production Stimulation of parasympathetic fibers increases saliva production small salivary glands secrete constantly the large salivary glands secrete only on stimulus (e.g. chemical, mechanical, etc.). Atrophy of the glandular parenchyma atrophy accompanies some systemic diseases, drug-induced, irradiation Consequence: hyposalivation - xerostomia ("dry mouth") Temporomandibular joint (art. temporomandibularis, TMJ) The connection between the mandible and the fixed temporal bone of the cranial base Fossa mandibularis + Tuberculum art. of temporal bone Caput mandibulae (condylus mandibulae) Discus articularis – cartilage plate Caput mandibulae (condylus mandibulae) – elongated ellipsoidal shape, elongated axis oriented horizontally on the condyle surface - thin plate of compact Inside is cancellous bone – trabeculles diverge from the center of the condyle radially to the surface During childhood trabeculles can contain islands of hyaline cartilage Microscopic structure of TMJ Fossa mandibularis • Plate of compact bone • The anterior border of mandibular fossa constitutes the tuberculum articulare - it has a similar structure to the caput mandibulae TMJ surfaces - fibrous cartilage • It is reinforced on the back of the tuberculum articulare • Cartilage better resists degeneration and has a good ability to regenerate Discus articularis • Ligament plate 3 - 4 mm thick • Its edges are fixed in a joint • Thinner in the middle - intermediate zone (1 - 1.5 mm) • Dense collagen tissue of a irregular type • In adulthood, it may contain islets of hyaline cartilage • Function: Stabilization and absorption of shocks and vibrations A: Articular layer B: Proliferative layer C: Chondrogenic layer D: Hypertrophic layer Mandibular condyle Complex inner structure Dorsal section is divided in 2 lamellae: Superior retrodiscal lamella of elastic fibers, which are inserted to dorsal edge of the fossa Inferior retrodiscal lamela inserts to the rear edge of condyle Between lamellae the retroauricular pillow of Zenker is present - areolar connective tissue with rich venous plexus (it is continuous by pterygoid plexus - plexus pterygoideus) Ventral section is thickenned and ends in places of insertion of lateral pterygoid muscle Thickened compartments act as stabilizing regions (wedges): stabilize condylus in the fossa Dorsal section Ventral section Discus articularis Retroauricular pillow of Zenker Joint capsule - free, especially on the medial side externally supported by the lateral and medial ligaments 2 layers: stratum fibrosum and stratum synoviale Articular cavity contains synovial fluid and is divided in two sections: upper - discotemporal lower - discomandibular Joint biomechanics: TMJ (articular disc) movements: https://www.youtube.com/watch?v=mB46 8Jh9aAY&ab_channel=AlilaMedicalMedia MRI: https://www.youtube.com/watch?v=ZnNg MnSfAws&ab_channel=SpringerVideos Temporomandibular joing (art. temporomandibularis, TMJ) Final form takes between 20 - 25 years of age Adaptability of TMJ – the ability to adapt to new functional requirements Very good in cartilage Poor in discus articularis a) Degenerative changes in the discus articularis, rupture or disintegration b) After the 5th decade perforation of the central disc part and connection of both sections of the articular cavity can occur Age changes in TMJ TMJ clicking: https://www.youtube.com/watch?v=Opgz2EUyI0w&ab_channel=WellingtonVillageOrthodonticsOttawa