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Development of the GI tract

Development of the GI tract. Sanjaya Adikari Dept. of Anatomy. Ampulla of Vater. Development of the GUT. Starts at 4 th week IUL due to flexion of embryo Formed by the endoderm lined yolk sac Epithelium and secretory components of glands derive from endoderm

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Development of the GI tract

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  1. Development of the GI tract SanjayaAdikari Dept. of Anatomy

  2. Ampulla of Vater

  3. Development of the GUT • Starts at 4th week IUL due to flexion of embryo • Formed by the endoderm lined yolk sac • Epithelium and secretory components of glands derive from endoderm • Muscles and connective tissues derive from splanchnic mesoderm • Primitive gut consists of four parts -Pharynx -Foregut -Midgut -Hindgut • Foregut, midgut and hindgut, each has its own artery

  4. Foregut Bucco-pharyngeal membrane Midgut Vitelline duct Allantois Cloacal membrane Hindgut

  5. Foregut Coeliac artery Midgut Sup. mesenteric artery Hindgut Inf. mesenteric artery

  6. Foregut • Supplied by Coeliac artery • Extends from the bucco-pharyngeal membrane to a point just distal to hepatic diverticulum • Its proximal part extends up to tracheo-bronchial diverticulum • Its distal part extends from TB diverticulum to HD • Derivatives:Pharynx, Oesophagus, stomach, liver, gall bladder, pancreas and duodenum up to duodenal papilla

  7. Development & rotation of stomach • Tube dilates, posterior wall grows rapidly than the anterior wall: Produce lesser & greater curvatures • Dorsal mesogastrium lengthens rapidly & forms greater omentum • Rotates 90 clock wise: left and right vagus nerves become anterior and posterior

  8. Rotation of stomach 90 rotation

  9. Development of spleen • Develops from the dorsal mesogastrium

  10. Development of duodenum • Develops from distal foregut & proximal midgut • Acquires ‘C’ shape due to stomach rotation and growth of pancreatic buds • Dorsal mesentery gets absorbed into posterior abdominal wall: 2nd and 3rd Parts becomes retroperitoneal with pancreas

  11. Development of liver & gall bladder • Liver parenchyma develops from liver bud/hepatic diverticulum • Connective tissue, Kupffer cells and haemopoietic tissue of liver develop from septum transversum • Gall bladder, cystic duct and common bile duct develop from cystic diverticulum

  12. Development of pancreas • Exocrine part develops from the ventral & dorsal pancreatic buds • Endocrine part (Islets of Langerhans) develop from the neural crest cells

  13. Hepatic diverticulum Cystic diverticulum Dorsal pancreatic bud Ventral pancreatic bud

  14. Accessory pancreatic duct Common bile duct Dorsal bud Uncinate process (ventral bud) Gall bladder Main pancreatic duct

  15. Midgut • Supplied by Superior mesenteric artery • Extends from the hepatic diverticulum to the junction of proximal 2/3 and distal 1/3 of the transverse colon • Connected to the yolk sac by vitelline duct through umbilical cord • Undergoes 270 rotation anticlockwise • Derivatives: Part of duodenum, small intestine, caecum, ascending colon and prox. 2/3 of transverse colon

  16. Midgut… • At 6th week I.U.L, mid gut loop herniates through the umbilical region – Physiological umbilical hernia • This is due to rapid increase in length relative to the size of the abdominal cavity • At 10th week I.U.L, it returns to the abdominal cavity • Rotates 90 when herniates and 180 when returns

  17. Hindgut • Supplied by Inferior mesenteric artery • Extends from the junction of proximal 2/3 and distal 1/3 of the transverse colon to Cloacal membrane • Derivates: Distal 1/3 of TC, descending colon, sigmoid colon, rectum and upper part of anus

  18. Perineum Coccyx Anal triangle subpubic angle Urogenital triangle

  19. Urorectal septum Cloaca Cloacal membrane Urorectal septum divides the cloaca into urogenital part and an anorectal part. This septum also divides the cloacal membrane into urogenitaland anal membranes. The septum itself becomes the perineal body.

  20. Developmental defects - Foregut • Pyloric stenosis: Hypertrophy of pyloric sphincter muscles • Atresia of bile duct: failure to recanalize the cystic diverticulum

  21. Developmental defects - Foregut • Duplication of gall bladder: formation of two cystic diverticula • Annular pancreas: mal fusion of ventral & dorsal pancreatic buds leading to duodenal stenosis

  22. Developmental defects - Midgut • Vitelline fistula: Persistence of vitelline duct • Vitelline cyst: Cyst formation with ligament on either side • Meckelsdiverticulum: Persistence of small part of vitelline duct connected to gut

  23. Developmental defects - Midgut • Omphalocoele: Persistence of physiological umbilical hernia/ non-return of intestinal loops at 10th week IUL

  24. Developmental defects - Hindgut • Imperforate anus: Nonrupture of anal membrane

  25. Developmental defects - Hindgut • Urorectal fistula: Persistent connection between urinary tract & rectum due to defective formation of urorectal septum

  26. Developmental defects - Hindgut • Congenital megacolon: Absence of parasympathetic ganglia in the bowel wall (aganglionicmegacolon or Hirschsprung disease)

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