MICROSCOPIC ANATOMY OF GIT oral cavity digestive tube Petr Vaňhara, PhD Department of Histology and Embryology LF MU pvanhara@med.muni.cz • Upper and lower lip • Vestibulum oris • Soft and hard palate • Tooth and gingiva • Tongue ORAL CAVITY ORAL MUCOSA • lamina epithelialis mucosae stratified squamous epithelium • lamina propria mucosae loose collagen C.T. Types of oral mucosa • lining mucosa - mucosal and submucosal C.T. • masticatory mucosa - parakeratinized epithelium - directly on periost (mucoperiosteum) - no submucosa • specialized mucosa - dorsum linguae – papillae LIP Mucosa Labial artery Labial glands M. orbicularis oris Labial skin Hair follicles M. orbicularis oris Vermillion border Ventral Dorsal Skin side (ventral) Oral side (dorsal) LIP Epidermis • Keratinized stratified squamous epithelium Dermis • Loose collagen C.T. • Hair follicles • Sebaceous glands • Sweat glands Oral mucosa • Stratified squamous epithelium • Loose collagen C.T. • Small salivary labial mixed glands LIP Vermillion border • Eleidin protein • salivary glands hair follicles, sweat glands absent • high c.t. papillae, capillaries • nerve endings, Meissner’s corpuscles torus labialis newborns pars glabra pars villosa TONGUE TONGUE TONGUE – APEX LINGUAE Dorsum linguae Facies mylohyoidea Musculi linguae Glandula lingualis anterior TONGUE – MUSCLES • Intraglossal • Extraglossal TONGUE – MUSCLES Extraglossal Intraglossal Septum linguae Aponeurosis linguae TONGUE – GLL. LINGUALES ANTERIORES (BLANDINI) TONGUE – FACIES MYLOHYOIDEA TONGUE – DORSUM LINGUAE • specialized mucosal structures - papillae • submucosal C.T. is absent TONGUE – FILLIFORM PAPILLAE TONGUE – FILLIFORM PAPILLAE TONGUE – FUNGIFORM PAPILLAE TONGUE – FUNGIFORM PAPILLAE TONGUE – FILLIFORM AND FUNGIFORM PAPILLAE TONGUE – FOLIATE PAPILLAE TONGUE – VALLATE PAPILLAE TONGUE – VALLATE PAPILLAE TONGUE – TASTE BUDS TONGUE – TASTE BUD • Intraepithelial • porus gustatorius • 2000-8000 in oral cavity • 60-80 cells • 70-80 m  30-40 m • microvilli on sensory cells • nerve fibers TONGUE – TASTE BUD doi.org/10.1016/j.neuron.2020.03.006 • secondary sensory epithelium I. II. • n. vagus • n. facialis • n. glossopharyngeus TONGUE – TASTE BUD • bitter • sweet • umami (glutamate) • G-protein-coupled receptors • salt • acid • ion channels • CD36 • fatty acid transporter • in taste sensing olfactory epithelium is involved TONGUE – RADIX, TONSILLA LINGUALIS TONGUE – RADIX, TONSILLA LINGUALIS TONGUE – RADIX, TONSILLA LINGUALIS, WEBER’S GLANDS PALATE SOFT PALATE SOFT PALATE SOFT PALATE – EPITHELIAL CHANGE TOOTH • Anatomical  clinical crown • Neck (cementoenamel junction) • Root DECIDUAL AND PERMANENT TEETH TOOTH – ENAMEL Enamel, 1-2 mm • Covers the crown • Made by ameloblasts, but after eruption acellular • No regeneration • 96% Ca-hydroxyapatite, enamel prisms • Enamelins, amelogenins, ameloblastins • Striae of Retzius (incremental growth lines) 10.1007/978-1-4020-5845-5_11 TOOTH – ENAMEL TOOTH – CEMENTUM Cementum, 100-500 µm • Covers root and neck • Cementoblasts/cementocytes • Regenerates • 50% Ca-hydroxyapatite • Collagen I, III, XII, GAGs, proteoglycans • Sharpey’s fibers – fibrilal cementum • Periodontal ligaments – tooth alveolus TOOTH – CEMENTUM TOOTH – DENTIN Dentin • Odontoblasts • Regenerates • 70% Ca-hydroxyapatite • Collagen I, glykoproteins, proteoglycans • Odontoblast processes –Tomes’ fibers • Owen’s lines • Von Ebner’s lines (incremental) • Nerve fibers TOOTH – DENTIN TOOTH – ODONTOBLASTS odontoblasts predentin dentin subodontoblastic zone pulp TOOTH – ODONTOBLASTS pulp odontoblasts predentin dentin cementum periodontium TOOTH – DENTIN cementum periodontium dentin subodontoblastic zone odontoblasty predentin TOOTH pulp dentin cementum periodontium bone TOOTH TOOTH – PULP • soft connnective tissue similar to embryonic mesenchyme • rich vascularisation and innervation • crown pulp and rooth canal • foramen apicale - periodontium • odontoblasts • nociceptive nerve plexus (plexus Raschkowi) https://www.slideshare.net/hesham63 /pulp-15597098 Gingiva ‐ free (marginal, g. libera) ‐ attached (g. affixa) ‐ paramarginal groove (outer gingival groove) ‐ sulcus gingivalis ‐ gingivodental junction of Gotlieb ‐ stratified squamous epithelium ‐ lamina propria mucosae – dense collagen c.t. TOOTH – PERIODONTIUM AND GINGIVA TOOTH – PERIODONTIUM AND GINGIVA • small (gll. labiales, buccales, retromolares, palatinae, gll. lingualis anterior, gll. Ebneri, gll. Weberi) • large (gl. parotis, gl. submandibularis, gl. sublingualis) SALIVARY GLANDS see next lecture SALIVARY GLANDS – GL. PAROTIS SALIVARY GLANDS – GL. PAROTIS SALIVARY GLANDS – GL. SUBMANDIBULARIS SALIVARY GLANDS – GL. SUBLINGUALIS PHARYNX • nasopharynx • oropharynx • laryngopharynx ALIMENTARY CANAL GENERAL ARCHITECTURE OF HOLLOW ORGANS 1. Mucosa (Tunica mucosa) 2. Submucosa (Tela submucosa) 3. Tunica muscularis externa 4. Serosa/adventitia Donna Myers © 2007 Lumen Serosa/Adventitia Muscularis externa Submucosa Mucosa GENERAL ARCHITECTURE OF HOLLOW ORGANS GENERAL ARCHITECTURE OF HOLLOW ORGANS GENERAL ARCHITECTURE OF HOLLOW ORGANS Mucosa (Tunica mucosa) - inner layer of digestive tube - protection, absorption and resorption - microscopic structure depending on localization - Lamina epithelialis mucosae - Lamina propria mucosae - Lamina muscularis mucosae GENERAL ARCHITECTURE OF HOLLOW ORGANS Lamina epithelialis mucosae - epithelium type corresponding to function of gut tube - oral cavity, pharynx, esophagus, anus – stratified squamous ep. - stomach, intestine – simple columnar - mucus - secreted by mucosal or submucosal glands (oral cavity, esophagus), secretory epithelium (stomach) or goblet cells (intestine) Lamina propria mucosae - Layer of mucosal connective tissue – loose collagen - Fenestrated blood capillaries – transport of metabolite (intestine) - mucosal glands in some regions /esophagus) - innervations, immune system Lamina muscularis mucosae - smooth muscle cells in several layers with variable orientation - small mechanical movements of mucosa facilitating secretion and absorption independently on peristaltic movements. Mucosa (Tunica mucosa) GENERAL ARCHITECTURE OF HOLLOW ORGANS Submucosa (Tela submucosa) - distinct layer of loose connective tissue - defines shape of mucosa (rugae, plicae) - larger blood and lymph veins nourishing mucosa, muscularis externa and serosa - innervation – nerve plexus - plexus submucosus Meissneri = groups of multipolar neurons and small ganglions, visceral sensory fibers (sympaticus) and fibers and terminal ganglions of parasympaticus (enteric nerve system) - glands – different in different regions - protective function GENERAL ARCHITECTURE OF HOLLOW ORGANS Outer muscular layers (Tunica muscularis externa) - Two concentric, thick layers of smooth muscle, separated by thin layer of connective tissue - Inner – circular, outer – longitudinal (spiral) - Myenteric (Auerbach) plexus - Peristaltic – passage through the gut tube - Local modifications of m.e. - pharyngoesophagal sphincter + external anal sphincter – skeletal muscles - stomach – third – oblique layer - taenie coli – thickened part of longitudinal layer in colon Circular Longitudinal GENERAL ARCHITECTURE OF HOLLOW ORGANS Serosa/Adventitia (Tunica serosa/adventitia) - outermost layer of gut tube - Serosa - serous membrane of loose connective tissue (Lamina propria serosae) and single layer squamous epithelium (L. epithelialis serosae) - syn. mesothelium, visceral peritoneum - continuous with mesenterium - barrier against various pathogens , antiadhesive properties – intracoelomic movements, immune functions (Ag presentation), ECM production, etc. - Adventitia - some parts of the tube are not covered with epithelium - esophagus in thorax, parts of digestive system in peritoneal cavity in sites of fixation to the walls (duodenum, part of colon, rectum, anal canal) - connective tissue only continuous with connective tissue of the walls GENERAL ARCHITECTURE OF HOLLOW ORGANS S.E. Mutsaers / The International Journal of Biochemistry & Cell Biology 36 (2004) 9–16 Serosa/Adventitia (Tunica serosa/adventitia) 1.4m GENERAL ARCHITECTURE OF HOLLOW ORGANS GENERAL ARCHITECTURE OF HOLLOW ORGANS Trachea Esophagus T. adventitia Paries membranaceus Cartilages Mucosa Muscularis externa https://hmb302.ca/chapters/respiratory-system/ Innervation of the digestive tube Enteric nervous system - self-contained nervous system - numerous ganglia, 100 x106 neurons (more than in spinal cord) - Meissner submucosal plexus and Auerbach myenteric plexus - peristaltic motility, secretory function, mucosal movements, regulation of blood flow - sensory components Parasympathetic and sympathetic supply • parasympathetic supply mostly by vagus nerve (cranial X), colon and rectum by sacral spinal nerves - vagus nerve – mostly sensory fibers (information from mucosa and back) - secretion from glands, smooth muscle contractions - inhibits sphincters, stimulates peristaltics and secretion • sympathetic supply by splanchnic nerves - vasomotor fibers – control of blood flow - activates sphincters, inhibits peristaltics and secretion GENERAL ARCHITECTURE OF HOLLOW ORGANS Plexus submucosus (Meissneri) GENERAL ARCHITECTURE OF HOLLOW ORGANS Enteric nervous system Plexus myentericus (Auerbachii) GENERAL ARCHITECTURE OF HOLLOW ORGANS Enteric nervous system MICROSCOPIC ANATOMY OF GIT - pars nasalis - pseudostratified columnar ciliated epithelium - seromucous glands - pars oralis et laryngea - nonkeratinized stratified squamous epithelium - mucous glands - collagen c.t. (lamina propria), typical tela submucosa absent - skeletal muscles PHARYNX - Mucosa - nonkeratinized stratified squamous epithelium → mechanically protects esophageal tissue - l. propria contains cardial glands (tubular mucinous) and diffuse lymphatic tissue - Submucosa - loose collagen connective tissue, defines shape of mucosa - blood and lymph veins, plexus submucosus Meissneri - submucosal glands (tubular mucinous) - diffuse lymphatic tissue ESOPHAGUS (OESOPHAGUS) - Muscularis externa - inner circular and outer longitudinal layer - plexus myentericus Auerbachi - upper third – skeletal muscle, mid third – mixed smooth and skeletal, lower third – smooth muscles only - Adventitia - neck and chest – connects esophagus with surrounding tissue - loose connective tissue - in peritoneal cavity - serosa ESOPHAGUS (OESOPHAGUS) Cardia of stomach – connection with esophagus ‐ Non-keratinized stratified squamous epithelium → simple columnar epithelium ‐ Change of mucosal architecture CARDIO-ESOPHAGEAL JUNCTION - general anatomy of hollow tube - anatomical regions differ in histologic structure – glands - rugae gastricae (submucosa) STOMACH (VENTRICULUS, GASTER) Stomach anatomy and microanatomy Gastric mucosa - simple columnar epithelium - surface epithelium produces mucus (mucinogenic granules, high content of HCO3 -, K+) = protective function - areae gastricae, foveolae gastricae STOMACH (VENTRICULUS, GASTER) Gastric mucosa - L. propria contains large amount of glands - Gl. cardiacae - Gl. pyloricae - Gl. gastricae propriae STOMACH (VENTRICULUS, GASTER) Gl. gastricae propriae - glands of fundus and body - simple tubular or branched - 2-4 opens to the gastric pits - four cell types of gl. gastricae propriae STOMACH (VENTRICULUS, GASTER) chief - most abundant, lower part of body and fundus of the gland - pyramidal shape, basophilic cytoplasm, RER, pepsinogenic granules parietal - neck-body junction - eosinophilic cytoplasm, high numbers of mtch., SER - complex and dynamic ultrastructure - intracellular canals in apical part with microvilli – membrane bound enzyme complexes producing H+ a Cl- (HCl originates extracelullarly) neck cells - cubic, mucinous - capable of regeneration of all cell types in gastric epithelium Gl. gastricae propriae STOMACH (VENTRICULUS, GASTER) Gl. gastricae propriae Type Hormone Localization/Function D cells Somatostatin - Stomach, intestine, hepatic and pancreatic ducts EC cells Serotonin - Stomach, gallbladder, intestine - Peristaltics ECL cells Histamin - Stomach - HCl secretion G cells Gastrin - Pars pylorica, duodenum - HCl, pepsin secretion L (EG) cells Enteroglucagon - Stomach, intestine - attenuates secretion of pancreatic enzymes and peristaltics enteroendocrine - minor, secretion - granules - different cell types with different sensitivity to various histological stainings - secretion of various biologically active compounds - DNES/APUD - GIT chemosensing STOMACH (VENTRICULUS, GASTER) Enteroendocrine system STOMACH (VENTRICULUS, GASTER) Parietal cell 10200 Parietal cell 100 000 H+/K+ ATPase inhibitors (Omeprazol) GENERAL ARCHITECTURE OF HOLLOW ORGANS GENERAL ARCHITECTURE OF HOLLOW ORGANS GASTRO-DUODENAL JUNCTION Four basic layers: mucosa, submucosa, muscularis externa, serosa mucosa and submucosa maximise the resorptive area • plicae circulares (Kerckringi) – mucosa + submucosa, ca 800, increase 2-3x, distal region of duodenum • villi (villi intestinales) – mucosa (l. propria + epithelium) 0,5-1,5 mm long, 10-40/mm2 , 4 000 000, increase 5-10x • microvilli – apical part of enterocytes – 1- 2 μm long, 0,1 μm wide, 100 mil./mm2, increase 20x SMALL INTESTINE – ADAPTATION TO EFFICIENT RESORPTION plicae circulares (Kerckringi) – 2-3x villi (villi intestinales) – 5-10x microvilli (striated border) – 20x Simple columnar epithelium - enterocytes - goblet cells - Paneth cells - enteroendocrine cells - M-cells Intestinal mucosa Crypts of Lieberkühn 200-600x SMALL INTESTINE – ADAPTATION TO EFFICIENT RESORPTION - simple tubular structures of intestinal mucosa, depth 0,3-0,5 mm - pass through l. propria and open to lumen - different cell types - secretion of digestive enzymes - epithelial renewal - enteroendocrine cells - immune response CRYPTS OF LIEBERKÜHN (GL. INTESTINALES) Enterocytes - tall, columnar cells - nucleus located in basis of the cell - apical surface modified- microvilli (3000) + glycocalyx (0,5m) = striated border (cuticle) - tight intercellular connections, interdigitations Function: - digestion – enzymatic complexes on microvilli membrane - absorption and transport – passive, facilitated i active - lipid uptake - chylomicrons 1m 0,1m CELLS OF INTESTINAL MUCOSA Microvilli CELLS OF INTESTINAL MUCOSA Transportion and resorption Transport of glucose from intestinal lumen to blood stream Na+/K+ ATPase - basolateral surface - concentration gradient Na+ and K+ K+ gradient generates negative membrane potential Na+/glucose symport on apical surface Facilitated diffusion by glucose uniporter (GLUT2) in basolateral membrane Acidification of stomach fluid by parietal cells Apical membrane - H+/K+ ATPase + Cl− a K+ canals Basolateral membrane – anion antiporter HCO3 − and Cl− ions Combined activity of ion channels a cells keeps the electroneutrality and neutral cytoplasmic pH while reaching high extracellular concentration of H+ and Cl− in lumen of stomach http://www.ncbi.nlm.nih.gov/books/NBK21502/ CELLS OF INTESTINAL MUCOSA Jádra F-aktin Mucin v sekrečních granulech - Cylindrical glandular epithelial cells - Apical surface – apocrine/merocrine secretion of mucin - Basal part – RER, GA, nucleus, mitochondria - Mucinogenic granules Goblet cells CELLS OF INTESTINAL MUCOSA Goblet cells CELLS OF INTESTINAL MUCOSA Paneth cells - basal part of crypts of Lieberkühn - basophilic cytoplasm - GA located above nucleus - acidophilic (red) granules - immune system - secretion granules contain biologically active substances e.g. lysozym) - influence intestinal microflora Enteroendocrine cells - similar to gastric enteroendocrine cells - regulate pancreatic secretions - homeostatic axis (brain-intestine-adipose tissue) - cholecystokinin, secretin, GIP, motilin, neurocrine peptides etc. CELLS OF INTESTINAL MUCOSA M cells (microfold) - epithelial cells above Peyer’s patches and lymphatic nodules - no microvilli - induces immune response - MHCII - antigen presentation to dendritic cells and lymphocytes „Microfold“ CELLS OF INTESTINAL MUCOSA Intestinal stem cells - bottom of crypts of Lieberkühn - epithelial renewal (4-5 days) - stem cell niche - role in cancer CELLS OF INTESTINAL MUCOSA L. propria - immune system – GALT - abundance of reticular fibers - immunologic barrier - Peyer’s patches INTESTINAL MUCOSA Brunner’s glands - gl. duodenale Brunneri - branched tuboalveolar glands - columnar mucinous cells - alkaline secretion - connective tissue reduced to thin septa between glandular lobules - open to crypts of Lieberkühn INTESTINAL SUBMUCOSA Muscularis externa - two layers of smooth muscle (inner circular, outer longitudinal) - plexus myentericus Auerbachi Serosa - loose collagen connective tissue + simple squamous epithelium (mesothelium) OUTER LAYERS OF INTESTINAL WALLS Intestinum crassum vs. intestinum tenue - plicae of Kerckring and villi absent - muscularis externa – longitudinal layer – taenie coli - surface serosa – appendices epiploicae (adipose) Small intestine Colon INTESTINUM CRASSUM – COLON - absorption of water, electrolytes - deeper crypts of Lieberkühn, no Paneth cells - abundant goblet cells - abundant lymphatic follicles in l. propria (GALT) INTESTINUM CRASSUM – COLON - develops from and is connected to caecum 8-10 cm (0,5-1cm) - continuous longitudinal layer of m. externa - lymphatic follicles reaching submucosa - irregular crypts of Lieberkühn with Paneth cells INTESTINUM CRASSUM – APPENDIX - Pars pelvina - plicae transversae recti - histological architecture identical to colon - Canalis analis - anulus hemorhoidalis – no L. crypts, simple columnar epithelium gradually replaced by stratified squamous epithelium - rich venous plexus - columnae rectales - sinus rectales and valvulae rectales - zona cutanea – typical skin RECTUM AND ANAL CANAL RECTUM AND ANAL CANAL Organ Region Mucosa Submucosa Muscularis externa Serosa/ AdventitiaLEM LPM LMM Esophag us 1/3 stratified squamous e. full gll. oesophageales skeletal A 2/3 glandulae oesophageae cardiacae both 3/3 smooth S Stomach cardia simple columnar e. gll. cardiacae full three layers oblique, circular, longitudinal S fundus/ corpus gll. gast. prop. gll. pyloricaepylorus Small intestine duoenum simple columnar e. brush border goblet cells L. crypts villi full gll. duodenales Brunneri A+S plicae circulares jejunum SPeyer’s plaque ileum Colon and rectum apendix simple columnar e. brush border goblet cells lymph. follicles partial lymph. nodes full S caecum villi absent full taeniae coli A+S colon A+S rektum columnae rectales A Canalis analis anorectal/ anocutaneous stratified squamous e. non- keratinized venous plexus partial- absent mucosal folds venous plexus inner anal sphincter A zona cutanea stratified squamous e. keratinized hair follicles, sweat glands THANK YOU FOR ATTENTION pvanhara@med.muni.cz http://www.histology.med.muni.cz