Digestive system 1. Microscopic anatomy of esophagus, stomach, small and large intestine 2. Microscopic anatomy of pancreas, liver, overview of GIT embryology 1. Microscopic anatomy of liver and bile ducts 2. Microscopic anatomy of pancreas 3. Embryonic development of digestive system, liver and pancreas - Macro – a microscopic anatomy - Definition and structure of liver lobulus - Hepatocytes and other liver cells - Intra- a extrahepatic bile ducts - Gall bladder - Pancreatic acini and ducts - Islets of Langerhans - Primitive gut derivatives - Changes in morphology and lovalization druing development - Regeneration LIVER (HEPAR) • Liver parenchyma – biggest gland in human body • C.t. capsule • Nutritive and functional blood supply • Endocrine and exocrine function • Uniform histology of all four major anatomic lobules and segments: - Hepatocytes and other cell types - C.t. stroma - Blood and lymphatic vessels - Sinusoids - Innervation - C.t. capsule - Serosa CAPSULA FIBROSA HEPATIS − Serous mesothelium − C.t. – collagen and elastic fibers − 70-100m − Porta hepatis CAPSULA FIBROSA HEPATIS Porta hepatis VASCULARISATION FUNCTION • capillary stream of stomach and intestine • vena portae • interlobular veins • circumlobular venules NUTRITIVE • aorta • arteria hepatica • segmental arteries • interlobular arteries • circumlobular arteriols • hepatic sinusoids • venae centrales hepatis • venae sublobulares • venae hepaticae • vena cava inferior 70% 30% IVC V. hepatica d. m. s. Porta hepatis VASKULARIZACE Gartner, Hiatt: Color Textbook of Histology (2001) MICROSCOPIC SEGMENTATION OF LIVER • Three possible definitions • Histological – lobulus venae centralis • Metabolic – liver acinus − metabolic zone 1 – 3 − oxygenation of hepatocytes • Historical (physiological) unit – lobulus venae interlobularis (portal acinus) wiki Liver acinus metabolic divergence dependent on arterio-venous gradients Zone I (periportal) Zone III (perivenous) oxidative processes glycogen synthesis beta-oxidation of fatty acids glycolysis catabolism of aminoacids lipogenesis gluconeogenesis ketogenesis production of urea production of glutamine synthesis of cholesterol synthesis of bile acids glycogenolysis biotransformation production of bile − Classical morphological unit − Polygonal cells (hexagonal), 0.7 x 2mm − Central vein − Radial cords of hepatocytes − Liver sinusoids − Portal triad, portobilliary region CENTRAL VEIN LOBULUS Lobulus venae centralis LALCENTRAL VEIN LOBULUS Lobulus venae centralis Contact of 3-4 neighboring lobuli • Interlobular artery (a. interlobularis) • Interlobular vein (v. interlobularis) • Interlobular bile duct (d. bilifer interlobularis) • Lymphatic vessels • Innervation – nervus vagus Loose interstitial c.t. CENTRAL VEIN LOBULUS Portal triad Ham: Textbook of Histology PORTAL TRIAD CENTRAL VEIN LOBULUS VENAE CENTRALIS • Hepatocytes arranged to cords, width 1-2 cells, often anastomoses • Sinusoids – 9-15m – Anastomosing network of flat endothelial cells – Basal membrane absent - no diffusion barrier – Fenestrations - 100nm, diaphragm absent – Intercellular space – Perisinusoidal (Dissé) apace – Reticular fibers, perisinusoidal fibroblasts – Dispersed Kupfer cells (monocytemacrophage system) – Perisinusoidal cells of Ito • Vena centralis – thin-walled vessel, draining blood from sinusoids LOBULUS VENAE CENTRALIS Hepatocytes and liver sinusoids • Space of Dissé – Connection of space of Dissé and sinusoidal lumen by fenestrated endothelium – Hepatocytes in direct contact with plasma (microvilli) – Cells of Ito LOBULUS VENAE CENTRALIS Hepatocytes and liver sinusoids LIVER SINUSOIDS INNER SURFACE OF LIVER SINUSOID – SEM KUPFFER CELLS • Liver macrophages • Mononuclear phagocyte system • Phagocytosis of particles, damaged erythrocytes and pathogens CELLS OF ITO • Star-shape (stellate, perisinusoidal) cells • Lipid droplets • Deposition of vitamin A • fine reticular c.t. • Antigen presenting cells (lipid antigens) HEPATOCYTES • Polygonal cells of liver parenchyma • 20x30m • Irregular trabecules between sinusoids • Usually one central nucleus. Bi- and multinuclear cells common (20%) • Nucleoli • Lysosomes • Glycogen • Functional surfaces: – Bile pole - secretory– membranes of neighboring hepatocytes form bile capillary – Blood pole - absorptive - sinusoidal – microvilli oriented to space of Dissé – Membranes with intercellular junctions HEPATOCYTES Long mitochondria with flat or tubular cristae Apparent RER, SER and Golgi Glycogen, lipid droplets, lysosomes, peroxisomes Erythrocyte Tight junction Bile capillary Kupfer cells Cells of Ito Nucleus Space of Dissé From plasma: Glucose, aminoacids, bile acids Blood proteins (serum albumin, fibrinogen, prothrombin, complement, transferrin, etc.) Space of Dissé Bile acids Bilirubin Steroids Drugs K+ Tight junction Bile capillary Cholestasis METABOLIC ACTVITY OF HEPATOCYTES • Synthesis and metabolism: − Proteosynthesis – RER + Golgi (plasma proteins – albumins, prothrombin, fibrinogen) − Metabolisms of lipids – SER, peroxisomes (lipidic conversion of fatty acids and glucose, lipoprotein synthesis) − Metabolism of glucose and saccharides - synthesis of glycogen, glycogenolysis and gluconeogenesis (insulin / glucagon) METABOLIC ACTIVITY OF HEPATOCYTES • Detoxication: SER (steroids, barbiturates, polyaromatic, lipid soluble compounds, etc., endo- and exotoxins) ROS • Peribilliary located lysosomes (autophagy, degradation of endocyted molecules) • Metabolism and deposition of vitamins and trace elements • Bile production: Recycling of bile acids (90%), 10% de novo synthesis, conjugation of toxic bilirubin and glukuronic acid to nontoxic complex bilirubin-glucuronid SER • Enterohepatic circulation − Resorption in terminal ileum − Vena portae − Sinusoids Hepatocytes − Bile capillaries − Intra and extrahepatic ducts − Duodenum Blood pole Bile pole INTRAHEPATIC AND EXTRAHEPATIC BILE DUCTS Bile capillaries (billiary canaliculli) - intercellular space between hepatocytes - 1-2m - no true wall, formed by membranes of hepatocytes - intercellular junctions Canals of Herring - simple squamous epithelium Interlobular bile ducts - cholangiocytes - cubic or low columnar epithelium + c.t. Lobar bile ducts - ductus hepaticus dexter et sinister - high simple columnar epithelium Ductus hepaticus, ductus cysticus, ductus choledochus - mucosa - fibromuscular layer INTRAHEPATIC EXTRAHEPATIC INTRAHEPATIC BILE DUCTS http://alexandria.healthlibrary.ca/documents/notes/bom/unit_4/unit%204%202005/L- 39%202008%20%20histology%20of%20the%20pancreas.xml INTRAHEPATIC BILE DUCTS INTRAHEPATIC BILE DUCTS INTRAHEPATIC BILE DUCTS TEM/SEM Central vein Circulobular venule Portal arteriole Interlobular bile ducts Cannal of Herring Bile capillary HEPATOCYTESCHOLANGIOCYTES Mucosa - lateral folds - simple columnar epithelium (cholangiocytes) - mucinous glands in c.t., goblet cells Fibromuscular layer - dense network of collagen and elastic fibers - leiomyocytes EXTRAHEPATIC BILE DUCTS d. hepaticus communis + d. cysticus  d. choledochus papilla duodeni major m. sphincter ampullae hepatoduodenalis (sphincter of Oddi) Bile modification GALL BLADDER (VESICA FELLEA) - Wall 1-2mm - Mucous coat - Muscle layer - Serosa/adventitia Mucous coat - mucosal folds - 20-50m simple columnar epithelium with microvilli - intercellular junctions - lamina propria mucosae - loose collagen c.t. with mucinous tuboalveolar glands - lamina muscularis mucosae absent Muscular layer (Muscularis propria) - 3D network of smooth muscle cells, - elastic fibers Large layer of subserous c.t. (l. propria serosae) Bile concentration - Bile secretion by liver– ca 0,8-1l daily - Gall bladder volume 15-60 ml - Water resorption GALL BLADDER (VESICA FELLEA) GALL BLADDER (VESICA FELLEA) mucosa Muscularis propria serosa GALL BLADDER (VESICA FELLEA) GALL BLADDER (VESICA FELLEA) PANCREAS • Compound, serous, tuboalveolar gland • Exocrine and endocrine character – pancreatic acinus – Islets of Langerhans • Major duct (Wirsungi) opens to Vater papilla as a common bile and pancreatic duct • Dense collagen c.t. capsule • Septs – blood cells, innervation, and interlobular ducts PANCREAS PANCREATIC ACINUS • Pyramidal epithelial cells • Pancreatic digestive enzymes • intercalated ducts • Serous acinar cells – Polarized secretory cells – Basophilic – Apex – Golgi and zymogenic granules – Microvilli – Intercellular junctions • Centroacinar cells – Centrally located nucleus, squamous character – Continuous with intercalated ducts PANCREATIC ACINUS PANCREATIC ACINUS PANCREATIC ACINUS • Centroacinar cells • Intercalated ducts – simple squamous epithelium + basal membrane • Intralobular and interlobular ducts – simple cubic – low columnar epithelium • Major pancreatic ducts – D. pancreaticus major – Wirsungi and D. pancreaticus accessorius - Santorini – bilayered columnar epithelium and dense collagen c.t. – intramural mucinous tubular glands, goblet cells, EC cells PANCREATIC DUCTS EXOCRINE FUNCTION OF PANCREAS • ca 1000-2000 ml daily • alkalic pH (8.8), HCO3 - (intercalated duct epithelium) • mucin (epithelium of large ducts) • Hydrolases – Trypsinogen – Chymotrypsinogen – Proelastases – Carboxypeptidases – Pancreatic lipase – Amylases – … Hormonal regulation (secretin, cholecystokinin) + parasympatikus ENDOCRINE FUNCTION OF PANCREAS Glucagon  Glycogen consumption in tissues and muscles  Increase of blood glucose Insulin  Increase of membrane permeability for glucose  Glucose oxidation in tissues  Decrease of blood glucose  Synthesis of glucan in muscles and liver Somatostatin  Inhibition of GIT hormones Pancreatic polypeptide  Autoregulation of pancreatic secretion ISLETS OF LANGERHANS • Clusters of pale cells • ca 1,5  106 • Thin c.t. capsule • Cords of epithelial cells • Sinusoids • General characteristics of APUD cells • A, B, D, PP cells A cells: 20%, glucagon B cells: 60-70%, insulin D cells: minor, somatostatin PP cells: minor, pancreatic polypeptide ISLETS OF LANGERHANS EMBRYONIC DEVELOPMENT OF LIVER AND PANCREAS EMBRYONIC DEVELOPMENT OF LIVER • Differentiation of endoderm and formation primitive gut • Growth factors of mesoderm determine identity of individual parts • Interactions with mesoderm of septum transversum and vv. omphalomesentericae EMBRYONIC DEVELOPMENT OF LIVER • Diverticulum of embryonic duodenum - liver diverticulum • Pars hepatica (parenchyma + ductus hepaticus) and pars cystica (ductus cysticus + gall bladder) form d. choledochus • Rapidly proliferating cells penetrate septum transversum (mesodermal plate between pericardial cavity and yolk sac) and growth into ventral mesentery • liver cords – parenchyma • Interactions between cells of liver cords and vv. omphalomesentericae induce development liver sinusoids • C.t. , Kupffer and hematopoieticcells – from mesoderm of septum transversum • Surface mesoderm differentiate into visceral peritoneum •10th week - 10% of body volume - hematopoiesis • 12th week - bile production EMBRYONIC DEVELOPMENT OF LIVER EMBRYONIC DEVELOPMENT OF LIVER In vivo In vitro Growth and differentiation factors (FGF, TGF, Wnt atd.) REGENERATION OF LIVER TISSUE - complex physiological response to damage of liver tissue - induction of proliferation and growth of liver parenchyma - hepatocyte proliferation - activation of endogenous progenitor cells - differentiation of exogenous multipotent cells - 6th week of development - two endodermal diverticula - dorsal and ventral duodenal diverticulum (= pancreas dorsale et ventrale) - after rotation of duodenal curve both diverticula fuse - ducts persist (ventral - major and dorsal - accessorius) - first ductal system develops - the secretory acini follow - cells that are not part of ductal structures differentiate into Islets of Langerhans - since 4th month in utero - secretory activity EMBRYONIC DEVELOPMENT OF PANCREAS EMBRYONIC DEVELOPMENT OF PANCREAS A – hESC  endoderm B – primitive gut C – foregut D – pancreatic precursors E – Insulin producing -buňky - General structure of a hollow organ. Microscopic anatomy of esophagus, stomach, intestine, rectum, canalis analis. Regional modification of general structure. Glands. Cell types and functions. - Microscopic anatomy of liver: endocrine and exocrine function of liver, vascularization, liver lobulus and its definition, liver cells, ultrastructure and function of hepatocytes, organization of intra- and extra-hepatic passages - Microscopic anatomy of pancreas: endocrine and exocrine function, pancreatic acinus and its ducts, ultrastructure and function of acinar cells, Islets of Langerhans and their structure, cell types of Islet of Langerhans and their function - Embryonic development and morphogenesis of digestive tube, liver and pancreas, primitive gut and its derivatives, esophagus, stomach, intestine. Flexion of embryo and rotation, liver and pancreatic diverticulum, differentiation of individual cell types. Summary of GIT II • Sadler: Langman’s Medical Embryology, 2000 • Ovalle&Nahirney: Netter’s Essential Histology, 2008 • Klika&Vacek: Histologie, 1974 • Ross&Pawlina: Histology (a text and atlas), 2011 • Ross&Romrell: Histology (a text and atlas), 1989 • Berman: Color Atlas of Basic Histology • Ústav histologie & embryologie LF MU, www.med.muni.cz/histology - LESSONS, LECTURES AND PRACTICALS • Čech S., Horký D., Sedláčková M.: Přehled embryologie člověka, Brno, LF MU, 2011 • Horký D., Čech S.: Mikroskopická anatomie, Brno, LF MU, 2011 • Lullmann-Rauch R.: Histologie, Grada 2012 • Ehrmann J., Hůlek P., et al. Hepatologie, Grada 2010 Study materials http://www.stembook.org/ Thank you for attention Petr Vaňhara, PhD Ústav histologie a embryologie LF MU pvanhara@med.muni.cz http://www.med.muni.cz/histology