Gastroduodenal Disease and Anatomy

Gastric Microscopic Anatomy	Top
Mucosa Epithelium Mucus-secreting cardia glands Oxyntic glands in the fundus and body Chief cells secrete pepsinogen Parietal cells secrete H+ and intrinsic factor Antrum and pylorus glands Both secrete HC03 and mucus G cells release gastrin D cells secrete somatostatin, inhibiting release of gastrin and H+

anatomy of the Duodenum
Most fixed portion of small bowel, surrounds head of the pancreas

Duodenal Microscopic Anatomy	Top
Mucosa Epithelium: enterocytes (absorptive), goblet cells, Paneth cells, enterochromaffin cells Lamina propria: contains Peyer’s patches (lymphoid aggregations with B cells in germinal centers and T cell in interfollicular zones) Muscularis mucosa Water and nutrients absorbed across the mucosa

• Inner Surface
  • Mucosal surface area specializations: microvilli, villi, plica circulares (valvulae conniventes)
  • Total absorptive surface: 200-550 cm2

 

Gastroduodenal Embryology

Top

Stomach has two mesenteries during development Dorsal mesogastrium, attached to the greater curvature, grows very redundant, overlaps, and becomes the greater omentum Ventral mesogastrium, part of the original septum transversum, becomes the following Lesser omentum (hepatogastric ligament) Peritoneal serosa of liver, gallbladder Falciform ligament, with embedded round ligament of the liver Greater curvature is initially dorsal, then the stomach rotates along its longitudinal axis until the dorsal curve lies to the left Stomach also rotates around an axis through the gastroesophageal junction, until the greater curvature lies in its final left inferolateral position Duodenum also rotates with the stomach, as well as around an anteroposterior axis, so that it surrounds the pancreas First two parts of the duodenum (down to the bile duct), the terminal portion of the foregut: supplied by the celiac axis Lower second through fourth parts of the duodenum, the initial segment of the midgut: supplied by the proximal superior mesenteric artery

Innervation

• Parasympathetic
  • Left vagal trunk lies anterior as it crosses the gastroesophageal junction and runs anteriorly along the lesser curvature toward the duodenum
  • Right vagal trunk lies posterior as it crosses the gastroesophageal junction and runs posteriorly along the lesser curvature toward the duodenum
  • Ganglion cells are located in myenteric (Auerbach’s) and submucosal (Meissner’s) plexuses in stomach and duodenum
• Sympathetic
  • Preganglionic fibers from T8-T10 lateral column distributed via splanchnic nerves
  • Postganglionic fibers are distributed from ganglion cells in celiac and superior mesenteric ganglia, traveling along respective arterial branches
• Sensory fibers (general visceral afferent)
  • Vagal afferents, including stretch, chemo-, and "satiety" receptors
  • Segmental afferents travel back parallel to sympathetics, through the celiac and superior mesenteric plexuses and the splanchnic nerves to thoracic spinal nerves, dorsal root ganglia, and spinal segments

 Gastritis

• Chronic
  • Type A: in fundus, associated with autoimmune disease and pernicious anemia
  • Type B: in antrum, associated with Helicobacter pylori

Peptic Ulcer :70%-80% in lesser curvature of the stomach
Hiatal Hernia - - - - - - Figure Top Type I: dilation of hiatus with sliding hernia; most common, may be associated with GERD, although most Type I patients do not reflux Type II: paraesophageal, hole in diaphragm next to the esophagus; symptoms - dysphagia, chest pain, early satiety Type III: combined Type IV: entire stomach in thorax, other organs may be included (e.g., spleen or colon)