1. Development of the GI tract
Sanjaya Adikari
Dept. of Anatomy

3. Ampulla of Vater

4. 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

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

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

11. 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

12. 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

13. Rotation of stomach
90 rotation

14. Development of spleen
Develops from the dorsal mesogastrium

16. 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

17. 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

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

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

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

21. 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

22. 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

23. 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

24. Perineum
Coccyx
Anal triangle
subpubic angle
Urogenital triangle

25. 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 urogenital and anal membranes.
The septum itself becomes the perineal body.

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

27. 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

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

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

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

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

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