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Stomach and small intestine 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 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) 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 ° 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 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 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,
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