Middle Digestive Tract

1. Stomach – embryogenesis and histogenesis 2. Small intestine – embryogenesis and histogenesis 3. Structural organization of the stomach and small intestine – macroscopic and microscopic anatomy 4. Roentgen anatomy of the stomach and small intestine 5. 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 V situated in the upper abdominal cavity, just below the diaphragm V 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: V develops from the foregut starting at the 4 th week V fusiform dilation of the foregut V rotates 90° clockwise around its longitudinal axis ° Histogenesis: V from the endoderm of the foregut: ‹ gastric epithelium o stratified columnar epithelium Ù simple columnar (2nd mo.) ‹ gastric glands ‹ gastric pits – middle of 2 nd mo. V 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: V the cardia, pars cardiaca – gastric orifice, ostium cardiacum V the fundus, fundus gastricus V the body, corpus gastricum V the pylorus, pars pylorica: ‹ pyloric antrum ‹ pyloric canal ‹ pyloric sphincter

V greater curvature, curvatura gastrica major V lesser curvature, curvatura gastrica minor Prof. Dr. Nikolai Lazarov 4 SPLANCHNOLOGY Topography of the stomach

° The skeletotopy: V in upper part of the abdominal cavity, under the left diaphragmatic vault ‹ in the left hypochondriac region ‹ partly in the epigastric region V the cardia – to the left of Th 10 -Th 11 vertebrae V the pylorus – to the right of Th 12 -L1 vertebrae

Prof. Dr. Nikolai Lazarov 5 SPLANCHNOLOGY Topography of the stomach

° The somatotopy – intraperitoneal position: V stomach bed (gastric chamber) V anterior gastric surface – 40 cm2 (beneath the Traube ’s space) Ù operative approach to the stomach V contact surfaces

Prof. Dr. Nikolai Lazarov 6 SPLANCHNOLOGY Wall of stomach ° Three major layers:

V the mucosa, tunica mucosa ‹ submucosa, tela submucosa V muscularis, tunica muscularis V the serosa, tunica serosa

Prof. Dr. Nikolai Lazarov 7 SPLANCHNOLOGY Wall of stomach ° Three major layers:

V the mucosa, tunica mucosa ‹ submucosa, tela submucosa V muscularis, tunica muscularis V the serosa, tunica serosa

Prof. Dr. Nikolai Lazarov 8 SPLANCHNOLOGY Histological structure

° Three distinct histological parts: V cardiac region ‹the cardia, pars cardiaca V fundic region ‹ the fundus and ‹ the body, corpus gastricum V pyloric region ‹the pylorus, pars pylorica

Prof. Dr. Nikolai Lazarov 9 SPLANCHNOLOGY Gastric mucosa

° mamillated areas, ° gastric folds (rugae), areae gastricae : plicae gastricae : V villous folds, plicae villosae V along the curvatures – V gastric pits longitudinal mucosal folds (foveolae gastricae ) V within lesser curvature – stomach road, “Magenstrasse” for gastric emptying

Prof. Dr. Nikolai Lazarov 10 SPLANCHNOLOGY Gastric mucosa

Prof. Dr. Nikolai Lazarov 11 SPLANCHNOLOGY Gastric mucosa

V lamina epithelialis – single-layered columnar epithelium: surface mucous cells (cell renewal 4-7 days) and pit cells V lamina propria mucosae – gastric glands V 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 V pepsinogen and hydrochloric acid V 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: V undifferentiated (stem) cells – in the upper neck region epitheliocyti nondifferentiati glandulae pyloricae V chief cells, exocrinocyti principales: pepsinogen and lypase V parietal cells, exocrinocyti parietales: HCl, intrinsic factor V mucous neck cells, mucocyti cervicales V enteroendocrine cells, endocrinocyti: gastrin , SOM, VIP, SER, histamine, ghrelin, bombesin

Prof. Dr. Nikolai Lazarov 14 SPLANCHNOLOGY Histological structure ° Gastric submucosa, tela submucosa: V dense connective tissue with blood and lymph vessels

° Gastric muscularis, tunica muscularis: V inner oblique layer, fibrae obliquae V middle circular layer (m. sphincter pyloricus) – poorly developed in the periesophageal region V outer longitudinal layer (stratum longitudinale) – absent from much of the anterior and ° Gastric serosa, tunica serosa: posterior stomach surfaces V part of peritoneum Prof. Dr. Nikolai Lazarov 15 SPLANCHNOLOGY Histological structure ° Gastric submucosa, tela submucosa: V dense connective tissue with blood and lymph vessels

° Gastric muscularis, tunica muscularis: V inner oblique layer, fibrae obliquae V middle circular layer (m. sphincter pyloricus) – poorly developed in the periesophageal region V outer longitudinal layer (stratum longitudinale) – absent from much of the anterior and ° Gastric serosa, tunica serosa: posterior stomach surfaces V part of peritoneum Prof. Dr. Nikolai Lazarov 16 SPLANCHNOLOGY Roentgen anatomy ° Saccus digestorius: Vfornix gastricus Vcorpus gastricum Vsinus ventriculi ° Canalis egestorius: Vpars pylorica Vpylorus

Prof. Dr. Nikolai Lazarov 17 SPLANCHNOLOGY Functional types of stomach

° Four major stomach types: V hypertonic (or short) stomach V orthotonic stomach V hypotonic (or long) stomach V atonic stomach Prof. Dr. Nikolai Lazarov 18 SPLANCHNOLOGY Vessels of the stomach

° Blood supply: by arteries from the celiac trunk ° Venous drainage: into the hepatic portal vein

Prof. Dr. Nikolai Lazarov 19 SPLANCHNOLOGY Lymphatic drainage ° from the medial ⅔ of the gastruc fundus and body to: V lymph nodes along the lesser gastric curvature V pericardial lymph nodes V posterior mediastinal lymph nodes ° from the rest of the fundus and body to: V pancreatic and splenic nodes ° from the lower gastric part to: V lymph nodes along the right gastro-omental artery V lymph nodes in the pyloric region V hepatic lymph nodes V superior mesenteric lymph nodes

Prof. Dr. Nikolai Lazarov 20 SPLANCHNOLOGY Innervation of the stomach ° gastric plexus, anterior and posterior:

V sympathetic – sympathetic trunk:

‹ splanchnic nerves

‹ coeliac ganglion

V parasympathetic – vagus nerve:

‹ gastric branches of anterior and

posterior vagal trunk V subserosal plexus, myenteric (Auerbach’s) plexus and submucosal (Meissner’s) plexus

Prof. Dr. Nikolai Lazarov 21 SPLANCHNOLOGY Small intestine, intestinum tenue

° Small intestine – convoluted tube: V initial part of the intestinal tract V extends from the pylorus to the ileocaecal valve V the longest component of the digestive tract – 6-8 m length V diameter – 4-3 cm V capacity – 4 l V the principal site for the digestion of food and for absorption of its products – functional peculiarities ° Three anatomic segments: V duodenum – 25-30 cm long V jejunum – 2.5 m long (first 2/5 of the total length of small bowel) V ileum – 3.5 m long (3/5 of the total length) Prof. Dr. Nikolai Lazarov 22 SPLANCHNOLOGY The duodenum, duodenum

° Localization and skeletotopy: V adherent to the posterior abdominal wall entirely above the level of the umbilicus V projected into the: ‹ epigastric region ‹ umbilical region V horseshoe-shaped; enclosing the head of the pancreas V immobile, has no mesentery ° Four anatomical parts:

V superior part, pars superior – 5 cm

V descending part, pars descendens – 7.5 cm

V horizontal part, pars horizontalis – 10 cm

V ascending part, pars ascendens – 2.5 cm Prof. Dr. Nikolai Lazarov 23 SPLANCHNOLOGY Duodenum in situ ° Duodenal position and relations:

V superior part – intraperitoneal position V descending part V horizontal part V ascending part – retroperitoneal position

Prof. Dr. Nikolai Lazarov 24 SPLANCHNOLOGY Duodenal wall

° Three major layers: V mucosa, tunica mucosa – impressively articulated relief ‹ plicae circulares (Kerkring’s folds) V submucous layer, tela submucosa V muscular layer, tunica muscularis V serosa, tunica serosa

Prof. Dr. Nikolai Lazarov 25 SPLANCHNOLOGY Duodenal mucosa ° Tunica mucosa: V villi V intestinal glands V duodenal glands

V lamina epithelialis – simple columnar epithelium V lamina propria – lymphocytes and lymphatic nodules (GALT) V lamina muscularis mucosae – smooth muscle fibers

Prof. Dr. Nikolai Lazarov 26 SPLANCHNOLOGY Intestinal villi, villi intestinales ° duodenal villi – a total of 4 million villi V 22-40/mm 2 – duodenum and jejunum, 18-31 /mm 2 – ileum V broad, leaf-like – in duodenum V long, slender but short – in mesenteric small intestine V epithelium – simple columnar absorptive (cell renewal 3-6 days) V stroma villi – loose connective tissue (lamina propria) ‹ lymphatic capillary, vas lymphaticum centrale ‹ blood vessels Ù network of fenestrated capillaries in the periphery ‹ smooth muscle cells – villi contact and shorten intermittently

Prof. Dr. Nikolai Lazarov 27 SPLANCHNOLOGY Intestinal villi, villi intestinales ° Surface epithelium – cell types: ‹enterocytes, epitheliocyti columnares – 90% of all cells Ù brush border (absorption) ‹goblet cells, exocrinocyti caliciformis – unicellular mucin-secreting glands ‹enteroendocrine cells – CCK, secretin and GIP

Prof. Dr. Nikolai Lazarov 28 SPLANCHNOLOGY Intestinal glands, glandulae intestinales ° Crypts of Lieberkühn – 150 million: V simple tubular glands, partially branched V secretion of intestinal juice, succus entericus V located in the lamina propria mucosae V 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 29 SPLANCHNOLOGY Duodenal glands, glandulae duodenales ° Brunner ’s glands: V branched compound tubular submucosal glands V mucus-rich alkaline secretion to protect the duodenal mucous membrane from the acidic gastric juice V cell types – eosinophilic with clear cytoplasm ‹ short columnar cells of mucous type ‹ goblet cells Ù mucin ‹ parietal cells ‹ Paneth cells ‹ enteroendocrine cells

Prof. Dr. Nikolai Lazarov 30 SPLANCHNOLOGY Duodenal wall ° Muscularis externa, tunica muscularis – well developed: V inner circular layer ‹ myenteric (Auerbach’s) nerve plexus V outer longitudinal layer ° Serosa, tunica serosa (adventitia): V simple squamous epithelium V blood and lymphatic vessels, nerve trunks

Prof. Dr. Nikolai Lazarov 31 SPLANCHNOLOGY Mesenteric small intestine

° Mesenteric small intestine: V intraperitoneal position V projected into the: ‹ mesogastric region ‹ hypogastric region ° The jejunum, jejunum: V horizontally oriented folds V to the left of median plane

V begins at the duodenojejunal flexure (L 2) ° The ileum, ileum: V vertically oriented folds V to the right of median plane

V extends to and ends at the ileocaecal valve (L 4)

Prof. Dr. Nikolai Lazarov 32 SPLANCHNOLOGY Histological structure of mucosa ° Mucosa, tunica mucosa: V laminaepithelialis – plicae circulares (Kerkring ’s folds/valves ) ‹ simple columnar (microvillous) absorptive epithelium ‹ intestinal villi and intestinal glands V 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 V lamina muscularis mucosae ‹ circular and longitudinal layers of smooth muscle cells ° submucosa, tela submucosa – well developed

Prof. Dr. Nikolai Lazarov 33 SPLANCHNOLOGY Histological structure of the wall

° Muscularis externa, tunica muscularis – peristalsis V inner circular layer – thick, bundles ‹ ileocaecal sphincter ‹ myenteric (Auerbach’s) nerve plexus V outer longitudinal layer – complete ° Subserosa, tela subserosa ° Serosa, tunica serosa – mesenterium: V blood and lymphatic vessels V nerves

Prof. Dr. Nikolai Lazarov 34 SPLANCHNOLOGY Blood supply of small intestine ° Duodenum – trunk celiac and superior mesenteric artery: V right gastric artery V hepatic artery proper and gastroduodenal artery V superior pancreaticoduodenal and V inferior pancreaticoduodenal arteries ° Mesenteric small intestine – superior mesenteric artery: V jejunal and ileal branches

Prof. Dr. Nikolai Lazarov 35 SPLANCHNOLOGY Venous drainage from intestinal wall

° Venous drainage from: V the duodenum – pancreaticoduodenal veins ‹ right Ù v. portae ‹ left Ù v. splenica (lienalis) V the mesenteric small intestine – vv. jejunales et ilei Ù v. portae

Prof. Dr. Nikolai Lazarov 36 SPLANCHNOLOGY

Lymphatic drainage from intestinal wall ° Lymphatic drainage from: V the duodenum ‹ pancreaticoduodenal lymph nodes ‹ hepatic lymph nodes V the mesenteric small intestine ‹ celiac lymph nodes ‹ mesenteric lymph nodes

Prof. Dr. Nikolai Lazarov 37 SPLANCHNOLOGY Innervation of small intestine

° coeliac plexus – duodenum ° myenteric (Auerbach’s) plexus and submucosal (Meissner’s) plexus – mesenteric small intestine

V sympathetic – sympathetic trunk:

‹ coeliac ganglion

‹ superior mesenteric ganglion

V parasympathetic – vagus nerve

‹ coeliac branches

‹ intestinal branches

Prof. Dr. Nikolai Lazarov 38 SPLANCHNOLOGY Voltaire (1694-1778)

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“The fate of a nation has often depended on the food or bad digestion of a prime minister ” Prof. Dr. Nikolai Lazarov 39