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Stomach and small intestine 1. 2. 3. 4. 5. Stomach – embryogenesis and histogenesis Small intestine – embryogenesis and histogenesis Structural organization of the stomach and small intestine – macroscopic and microscopic anatomy Roentgen anatomy of the stomach and small intestine Blood supply and innervation of the stomach and small intestine SPLANCHNOLOGY Stomach – gaster, ventriculus The most dilated (J-shaped) part of the digestive tube – 1-1.7 l situated in the upper abdominal cavity, just below the diaphragm storage and break food down, and mixing it with juices secreted by its lining – chemical digestion Prof. Dr. Nikolai Lazarov 2 SPLANCHNOLOGY Embryonic development Embryogenesis: develops from the foregut starting at the 4th week fusiform dilation of the foregut rotates 90° clockwise around its longitudinal axis Histogenesis: from the endoderm of the foregut: gastric epithelium o stratified columnar epithelium simple columnar (2nd mo.) gastric glands gastric pits – middle of 2nd mo. from the surrounding mesenchyme: connective tissue components o serosa – 2nd mo. (splanchnopleural mesoderm) smooth muscles – 2nd – 4th mo. Prof. Dr. Nikolai Lazarov 3 SPLANCHNOLOGY Macroscopic anatomy Four distinct anatomical regions: the cardia, pars cardiaca – gastric orifice, ostium cardiacum the fundus, fundus gastricus the body, corpus gastricum the pylorus, pars pylorica: pyloric antrum pyloric canal pyloric sphincter greater curvature, curvatura gastrica major lesser curvature, curvatura gastrica minor Prof. Dr. Nikolai Lazarov 4 SPLANCHNOLOGY Topography of the stomach The skeletotopy: in upper part of the abdominal cavity, under the left diaphragmatic vault in the left hypochondriac region partly in the epigastric region the cardia – to the left of Th10-Th11 vertebrae the pylorus – to the right of Th12-L1 vertebrae Prof. Dr. Nikolai Lazarov 5 SPLANCHNOLOGY Topography of the stomach The somatotopy – intraperitoneal position: stomach bed (gastric chamber) anterior gastric surface – 40 cm2 (beneath the Traube’s space) operative approach to the stomach contact surfaces Prof. Dr. Nikolai Lazarov 6 SPLANCHNOLOGY Wall of stomach Three major layers: the mucosa, tunica mucosa submucosa, tela submucosa muscularis, tunica muscularis the serosa, tunica serosa Prof. Dr. Nikolai Lazarov 7 SPLANCHNOLOGY Wall of stomach Three major layers: the mucosa, tunica mucosa submucosa, tela submucosa muscularis, tunica muscularis the serosa, tunica serosa Prof. Dr. Nikolai Lazarov 8 SPLANCHNOLOGY Histological structure Three distinct histological parts: cardiac region the cardia, pars cardiaca fundic region the fundus and the body, corpus gastricum pyloric region the pylorus, pars pylorica Prof. Dr. Nikolai Lazarov 9 SPLANCHNOLOGY Gastric mucosa mamillated areas, areae gastricae: villous folds, plicae villosae gastric pits (foveolae gastricae) gastric folds (rugae), plicae gastricae: along the curvatures – longitudinal mucosal folds within lesser curvature – stomach road, “Magenstrasse” for gastric emptying Prof. Dr. Nikolai Lazarov 10 SPLANCHNOLOGY Gastric mucosa mamillated areas, areae gastricae: villous folds, plicae villosae gastric pits (foveolae gastricae) gastric folds (rugae), plicae gastricae: along the curvatures – longitudinal mucosal folds within lesser curvature – stomach road, “Magenstrasse” for gastric emptying Prof. Dr. Nikolai Lazarov 11 SPLANCHNOLOGY Gastric mucosa lamina epithelialis – single-layered columnar epithelium: surface mucous cells (cell renewal 4-7 days) and pit cells lamina propria mucosae – gastric glands lamina muscularis mucosae – causes changes in the mucosal surface relief Prof. Dr. Nikolai Lazarov 12 SPLANCHNOLOGY Gastric glands proper gastric (fundic) glands ~35 million glandulae gastricae propriae pepsinogen and hydrochloric acid gastric intrinsic factor cardiac glands – glandulae cardiacae pyloric glands – glandulae pyloricae, ~3.5 million (total secretory surface of 0.4 m2) Prof. Dr. Nikolai Lazarov 13 SPLANCHNOLOGY Gastric glands proper gastric (fundic) glands – parts: isthmus, neck and base (pars principalis) cell types: undifferentiated (stem) cells – in the upper neck region epitheliocyti nondifferentiati glandulae pyloricae chief cells, exocrinocyti principales: pepsinogen and lypase parietal cells, exocrinocyti parietales: HCl, intrinsic factor mucous neck cells, mucocyti cervicales enteroendocrine cells, endocrinocyti: gastrin, SOM, VIP, SER, histamine, ghrelin, bombesin Prof. Dr. Nikolai Lazarov 14 SPLANCHNOLOGY Histological structure Gastric submucosa, tela submucosa: dense connective tissue with blood and lymph vessels Gastric muscularis, tunica muscularis: inner oblique layer, fibrae obliquae middle circular layer (m. sphincter pyloricus) – poorly developed in the periesophageal region outer longitudinal layer (stratum longitudinale) – absent from much of the anterior and posterior stomach surfaces Gastric serosa, tunica serosa: part of peritoneum Prof. Dr. Nikolai Lazarov 15 SPLANCHNOLOGY Roentgen anatomy Saccus digestorius: fornix gastricus corpus gastricum sinus ventriculi Canalis egestorius: pars pylorica pylorus Prof. Dr. Nikolai Lazarov 16 SPLANCHNOLOGY Functional types of stomach Four major stomach types: hypertonic (or short) stomach orthotonic stomach hypotonic (or long) stomach atonic stomach Prof. Dr. Nikolai Lazarov 17 SPLANCHNOLOGY Vessels of the stomach Blood supply: by arteries from the celiac trunk Venous drainage: into the hepatic portal vein Prof. Dr. Nikolai Lazarov 18 SPLANCHNOLOGY Lymphatic drainage from the medial ⅔ of the gastruc fundus and body to: lymph nodes along the lesser gastric curvature pericardial lymph nodes posterior mediastinal lymph nodes from the rest of the fundus and body to: pancreatic and splenic nodes from the lower gastric part to: lymph nodes along the right gastro-omental artery lymph nodes in the pyloric region hepatic lymph nodes superior mesenteric lymph nodes Prof. Dr. Nikolai Lazarov 19 SPLANCHNOLOGY Innervation of the stomach gastric plexus, anterior and posterior: sympathetic – sympathetic trunk: splanchnic nerves coeliac ganglion parasympathetic – vagus nerve: gastric branches of anterior and posterior vagal trunk subserosal plexus, myenteric (Auerbach’s) plexus and submucosal (Meissner’s) plexus Prof. Dr. Nikolai Lazarov 20 SPLANCHNOLOGY Small intestine, intestinum tenue Small intestine – convoluted tube: initial part of the intestinal tract extends from the pylorus to the ileocaecal valve the longest component of the digestive tract – 6-8 m length diameter – 4-3 cm capacity – 4 l the principal site for the digestion of food and for absorption of its products – functional peculiarities Three anatomic segments: duodenum – 25-30 cm long jejunum – 2.5 m long (first 2/5 of the total length of small bowel) ileum – 3.5 m long (3/5 of the total length) Prof. Dr. Nikolai Lazarov 21 SPLANCHNOLOGY The duodenum, duodenum Localization and skeletotopy: adherent to the posterior abdominal wall entirely above the level of the umbilicus projected into the: epigastric region umbilical region horseshoe-shaped; enclosing the head of the pancreas immobile, has no mesentery Four anatomical parts: superior part, pars superior – 5 cm descending part, pars descendens – 7.5 cm horizontal part, pars horizontalis – 10 cm ascending part, pars ascendens – 2.5 cm Prof. Dr. Nikolai Lazarov 22 SPLANCHNOLOGY Duodenum in situ Duodenal position and relations: superior part – intraperitoneal position descending part horizontal part ascending part – retroperitoneal position Prof. Dr. Nikolai Lazarov 23 SPLANCHNOLOGY Duodenal wall Three major layers: mucosa, tunica mucosa – impressively articulated relief plicae circulares (Kerkring’s folds) submucous layer, tela submucosa muscular layer, tunica muscularis serosa, tunica serosa Prof. Dr. Nikolai Lazarov 24 SPLANCHNOLOGY Duodenal mucosa Tunica mucosa: villi intestinal glands duodenal glands lamina epithelialis – simple columnar epithelium lamina propria – lymphocytes and lymphatic nodules (GALT) lamina muscularis mucosae – smooth muscle fibers Prof. Dr. Nikolai Lazarov 25 SPLANCHNOLOGY Intestinal villi, villi intestinales duodenal villi – a total of 4 million villi 22-40/mm2 – duodenum and jejunum, 18-31 /mm2 – ileum broad, leaf-like – in duodenum long, slender but short – in mesenteric small intestine epithelium – simple columnar absorptive (cell renewal 3-6 days) stroma villi – loose connective tissue (lamina propria) lymphatic capillary, vas lymphaticum centrale blood vessels network of fenestrated capillaries in the periphery smooth muscle cells – villi contract and shorten intermittently Prof. Dr. Nikolai Lazarov 26 SPLANCHNOLOGY Intestinal villi, villi intestinales Surface epithelium – cell types: enterocytes, epitheliocyti columnares – 90% of all cells brush border (absorption) goblet cells, exocrinocyti caliciformis – unicellular mucin-secreting glands enteroendocrine cells – CCK, secretin and GIP Prof. Dr. Nikolai Lazarov 27 SPLANCHNOLOGY Intestinal glands, glandulae intestinales Crypts of Lieberkühn – 150 million: simple tubular glands, partially branched secretion of intestinal juice, succus entericus located in the lamina propria mucosae Cell types in the crypt epithelium: columnar intestinal cells, enterocytes undifferentiated columnar cells – stem cells (mitoses) typical goblet cells – acid glycoproteins of the mucin Paneth cells – lysozyme, glycoproteins, several peptidases enteroendocrine cells – APUD cells, DNES, GEP system Prof. Dr. Nikolai Lazarov 28 SPLANCHNOLOGY Duodenal glands, glandulae duodenales Brunner’s glands: branched compound tubular submucosal glands mucus-rich alkaline secretion to protect the duodenal mucous membrane from the acidic gastric juice cell types – eosinophilic with clear cytoplasm short columnar cells of mucous type goblet cells mucin parietal cells Paneth cells enteroendocrine cells Prof. Dr. Nikolai Lazarov 29 SPLANCHNOLOGY Duodenal wall Muscularis externa, tunica muscularis – well developed: inner circular layer myenteric (Auerbach’s) nerve plexus outer longitudinal layer Serosa, tunica serosa (adventitia): simple squamous epithelium blood and lymphatic vessels, nerve trunks Prof. Dr. Nikolai Lazarov 30 SPLANCHNOLOGY Mesenteric small intestine Mesenteric small intestine: intraperitoneal position projected into the: mesogastric region hypogastric region The jejunum, jejunum: horizontally oriented folds to the left of median plane begins at the duodenojejunal flexure (L2) The ileum, ileum: vertically oriented folds to the right of median plane extends to and ends at the ileocaecal valve (L4) Prof. Dr. Nikolai Lazarov 31 SPLANCHNOLOGY Histological structure of mucosa Mucosa, tunica mucosa: lamina epithelialis – plicae circulares (Kerkring’s folds/valves) simple columnar (microvillous) absorptive epithelium intestinal villi and intestinal glands lamina propria – loose connective tissue blood and lymphatic vessels, muscle of Brücke solitary lymphatic nodules – scattered throughout aggregated lymphatic nodules (Payer’s patches) – in ileum lamina muscularis mucosae circular and longitudinal layers of smooth muscle cells submucosa, tela submucosa – well developed Prof. Dr. Nikolai Lazarov 32 SPLANCHNOLOGY Histological structure of the wall Muscularis externa, tunica muscularis – peristalsis inner circular layer – thick, bundles ileocaecal sphincter myenteric (Auerbach’s) nerve plexus outer longitudinal layer – complete Subserosa, tela subserosa Serosa, tunica serosa – mesenterium: blood and lymphatic vessels nerves Prof. Dr. Nikolai Lazarov 33 SPLANCHNOLOGY Blood supply of small intestine Duodenum – the celiac trunk and superior mesenteric artery: right gastric artery hepatic artery proper and gastroduodenal artery superior pancreaticoduodenal and inferior pancreaticoduodenal arteries Mesenteric small intestine – superior mesenteric artery: jejunal and ileal branches Prof. Dr. Nikolai Lazarov 34 SPLANCHNOLOGY Venous drainage from intestinal wall Venous drainage from: the duodenum – pancreaticoduodenal veins right v. portae left v. splenica (lienalis) the mesenteric small intestine – vv. jejunales et ilei v. portae Prof. Dr. Nikolai Lazarov 35 SPLANCHNOLOGY Lymphatic drainage from intestinal wall Lymphatic drainage from: the duodenum pancreaticoduodenal lymph nodes hepatic lymph nodes the mesenteric small intestine celiac lymph nodes mesenteric lymph nodes Prof. Dr. Nikolai Lazarov 36 SPLANCHNOLOGY Innervation of small intestine coeliac plexus – duodenum myenteric (Auerbach’s) plexus and submucosal (Meissner’s) plexus – mesenteric small intestine sympathetic – sympathetic trunk: coeliac ganglion superior mesenteric ganglion parasympathetic – vagus nerve coeliac branches intestinal branches Prof. Dr. Nikolai Lazarov 37 SPLANCHNOLOGY Voltaire (1694-1778) Thank you ... “The fate of a nation has often depended on the food or bad digestion of a prime minister” Prof. Dr. Nikolai Lazarov 38