Development of Gastrointestinal system & its associated developmental anomalies- PDF Lecture notes by Dr.N.Mugunthan
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The document is a detailed lecture on the development of the digestive system, covering the foregut, midgut, and hindgut, along with their congenital anomalies. It explains the formation of the primitive gut, its subdivisions, blood supply, and specific developmental processes of organs like the esophagus, stomach, liver, pancreas, and intestines. It also discusses various developmental anomalies associated with each section of the digestive tract.
Development of Gastrointestinal system & its associated developmental anomalies- PDF Lecture notes by Dr.N.Mugunthan
- 1. DEVELOPMENT OF DIGESTIVE SYSTEM Lecture By Dr.N.Mugunthan. MBBS, MS, DNB, MNAMS, PhD, Professor, MGMC&RI.
- 2. LEARNING OBJECTIVES Development of Foregut & its congenital anomalies Midgut & its congenital anomalies Hindgut & its congenital anomalies © Dr.N.Mugunthan
- 3. GENERAL CONCEPT - GIT Formation of Primitive Gut Primitive Gut- endo dermal Yolk sac (dorsal part) Ventral part – extraembryonic yolk sac Connected by vitello- intestinal duct Bucco-pharyngeal membrane Cloacal membrane © Dr.N.Mugunthan
- 4. GIT -4 layer (inner to outer) 1. Mucosa (epithelium, lamina propria & muscularis interna) 2. Submucosa 3. Muscularis externa 4. Serosa GENERAL CONCEPT – GIT CONT… © Dr.N.Mugunthan
- 5. PRIMITIVE GUT TUBE Subdivision 1. Fore gut – prelaryngeal & postlaryngeal part 2. Mid gut – prearterial & postarterial segment 3. Hind gut – preallontoic & postallontaoic part Junction between foregut & midgut - anterior intestinal portal. Junction between midgut & hindgut - posterior intestinal portal. © Dr.N.Mugunthan
- 6. BLOOD VESSEL OF PRIMITIVE GUT The midline artery- dorsal aorta. Artery of fore gut-celiac artery. Artery of mid gut-superior mesenteric artery. Artery of hind gut- inferior mesenteric artery © Dr.N.Mugunthan
- 7. DERIVATIVES OF FORE GUT Pre-laryngeal part Floor of the mouth Tongue Pharynx Derivatives of pharyngeal pouches Thyroid Respiratory system Post-laryngeal part Esophagus Stomach Proximal half of the duodenum(up to the opening of Bile duct). Liver, biliary apparatus & pancreas © Dr.N.Mugunthan
- 8. DEVELOPMENT OF ESOPHAGUS From part of the foregut between pharynx and stomach. Ventrally-laryngotracheal groove bulges to form tracheoesophageal septum. Which divides the foregut caudal to the pharynx into trachea and esophagus. © Dr.N.Mugunthan
- 9. Initially the esophagus is short. Elongation is due to 1.Formation of neck. 2.Descent of diaphragm, heart & lung. o Lining epithelium - endoderm. o Musculature –splanchnic mesoderm. Upper 1/3rd –striated muscle only. Middle 1/3rd - striated and smooth muscle Lower 1/3rd -smooth muscle only DEVELOPMENT OF ESOPHAGUS CONT… © Dr.N.Mugunthan
- 10. ESOPHAGUS – DEVELOPMENTAL ANOMALIES Esophageal atresia- failure of recanalization / often associated with tracheo-esophageal fistula Tracheo-esophageal fistula –different types Achalasia cardia – agenesis of nerve cells in myenteric and submucous plexus © Dr.N.Mugunthan
- 11. 4th Week Stomach appears as a fusiform dilatation distal to the esophagus. Borders: ventral (lesser curvature ) & dorsal (grows rapidly –greater curvature) Changes in Shape Surfaces: right & left Ventral Mesogastrium. Dorsal Mesogastrium. DEVELOPMENT OF STOMACH CONT… © Dr.N.Mugunthan
- 12. DEVELOPMENT OF STOMACH CONT… Changes in Position Rotation to right (clockwise 90°)- around a vertical axis Left surface becomes anterior. Right surface becomes posterior. Cephalic and caudal ends lie in the Midline. As a result of this rotation- left & right vagus becomes anterior and posterior vagus. © Dr.N.Mugunthan
- 13. DEVELOPMENT OF STOMACH CONT… Rotation around its Antero posterior axis Cardiac end moves to left and downward Pyloric end moves to the right and upward © Dr.N.Mugunthan
- 14. DERIVATIVES OF VENTRAL MESOGASTRIUM Ventral mesogastrium: Extends from the lesser curvature to septum transversum and anterior abdominal wall Derivatives: Falciform ligament Right and left triangular ligaments. Superior and inferior layers of coronary ligaments Lesser omentum.© Dr.N.Mugunthan
- 15. DERIVATIVES OF DORSAL MESOGASTRIUM Dorsal mesogastrium: Extends from the greater curvature to the posterior abdominal wall. Derivatives: Spleen. Gastrosplenic omentum Lienorenal ligament. Greater omentum © Dr.N.Mugunthan
- 16. Congenital hypertrophic pyloric stenosis • Abnormal thickening of circular layer of muscularis externa (pyloric sphincter) • Infant prsented with distention of stomach & projectile vomiting. • Surgical relief of the pyloric obstruction by - Pyloromyotomy STOMACH – DEVELOPMENTAL ANOMALIES © Dr.N.Mugunthan
- 17. DUODENUM 2 sources Fore gut & midgut Fore gut- 1st & 2nd part up to the opening of ampulla of vater. Midgut -2nd part below the opening of ampulla of vater, 3rd & 4th part. Duodenum forms a sagittal loop ( with ventral convexity) attached to posterior abdominal wall by mesoduodenum. © Dr.N.Mugunthan
- 18. DUODENUM CONT… 3 phases of development 1.Rotation 2. Fixation 3. Axial rotation (2nd part only) 1. Clockwise rotation: Sagitally placed loop fall on the right side Right surface becomes posterior (retroperitoneal) / left becomes anterior 2. Fixation: Mesoduodenum is absorbed by Zygosis and becomes retro- peritoneal. 3. Axial rotation (2nd part only) Around a vertical axis © Dr.N.Mugunthan
- 19. 8th week – lumen is obliterated by proliferation of lining endodermal cells 3rd month end – lumen is recanalised DUODENUM CONT… © Dr.N.Mugunthan
- 20. Duodenal atresia a) Failure of recanalaisation b) Annular pancreas Common site –below hepatopancreatic ampulla DUODENUM – DEVELOPMENTAL ANOMALIES © Dr.N.Mugunthan
- 21. DEVELOPMENT OF LIVER & BILIARY APPARATUS 4th week An endodermal diverticulum – hepatic bud Arises from terminal part of foregut (ventral border of duodenum) Grows into ventral mesogastrium & reaches septum transversum Hepatic bud divides into right & left © Dr.N.Mugunthan
- 22. Endodermal cell – hepatocytes (parenchyma) Mesenchyme of septum transversum – fibroareolar stroma of liver Stalk of hepatic bud forms – bile duct Its 2 branches forms –right & left hepatic ducts Cystic bud develops from the bile duct Cystic bud –becomes gall bladder & cystic duct Axial rotation of 2nd part of duodenum- bile duct open into post.medial aspect of 2nd part of duodenum along with ventral pancreatic duct DEVELOPMENT OF LIVER & BILIARY APPARATUS CONT… © Dr.N.Mugunthan
- 23. 1. Atretic gall bladder 2. Septate gall bladder 3. Double gall bladder 4. Intra hepatic gall bladder 5. Mobile or floating gall bladder 6. Hepatocystic communications 7. Hartmanns pouch 8. Absence of cystic duct 9. Atresia of bile duct 10. Absence of hepato- pancreatic ampulla BILIARY APPARATUS – DEVELOPMENTAL ANOMALIES © Dr.N.Mugunthan
- 24. DEVELOPMENT OF PANCREAS 2 Endodermal pancreatic buds 1. Dorsal pancreatic bud (dorsal wall of caudal part of foregut -dorsal mesentry of duodenum ) 2. Ventral pancreatic bud (ventral wall of caudal part of foregut ) Bilobed structure, later fused –single mass © Dr.N.Mugunthan
- 25. Rotation of duodenum to right (C shaped ) Ventral pancreatic bud –Right side. Dorsal pancreatic bud – Left side. Axial rotation of 2nd part of duodenum- ventral bud appears on post.medial aspect of 2nd part of duodenum along with bile duct Fusion of both buds takes place DEVELOPMENT OF PANCREAS CONT… © Dr.N.Mugunthan
- 26. • Derivatives of dorsal pancreatic bud - upper part of head, neck,body and tail • Derivatives of ventral pancreatic bud - lower part of head (uncinate process ) DEVELOPMENT OF PANCREAS CONT… © Dr.N.Mugunthan
- 27. Development of Pancreatic duct: Initially the ducts of ventral & dorsal buds open separately into the duodenum. Ventral pancreatic duct open with bile duct. Communication develops between dorsal and ventral buds. DEVELOPMENT OF PANCREAS CONT… © Dr.N.Mugunthan
- 28. Main pancreatic duct (Wirsung)- a.Dorsal pancreatic duct distal to anastomosis b.Anastomotic duct. c.Ventral Pancreatic duct proximal to the anastomosis. Accessory pancreatic duct (Santorini)- Persistence of proximal part of dorsal pancreatic duct DEVELOPMENT OF PANCREAS CONT… © Dr.N.Mugunthan
- 29. Annular Pancreas: 2 lobes of ventral pancreatic bud grow and migrate in opposite directions around the 2nd part of duodenum Forms a collar of Pancreatic tissue before fuses with dorsal bud Features: Duodenal obstruction Vomiting Treatment - duodeno- jejunostomy PANCREAS– DEVELOPMENTAL ANOMALIES © Dr.N.Mugunthan
- 30. DERIVATIVES OF MIDGUT Pre-arterial segment (Cephalic) Lower part of the duodenum (caudal to the bile duct opening) Jejunum Most of ileum. Post-arterial segment (Caudal) Terminal part of ileum Caecum Appendix Ascending colon Right 2/3 of the transverse colon. © Dr.N.Mugunthan
- 31. Superior retention band – attachment of dorsal end of cephalic limb (future duodeno-jejunal flexure) to body wall by mesenchymal condensation of dorsal mesentery – persist as suspensory muscle of duodenum or ligament of Treitz. Inferior retention band – attachment of dorsal end of caudal limb (colic angle) to body wall – persist as phrenico- colic ligament. DERIVATIVES OF MIDGUT CONT… © Dr.N.Mugunthan
- 32. DEVELOPMENT OF INTESTINES 5th week Umbilical herniation (physiological) Movement of intestines into the umbilicus (extraembryonic part of coelomic cavity) as it elongates. Remains till 10th week © Dr.N.Mugunthan
- 33. ROTATION OF MIDGUT First stage (within umbilical sac) Anticlock wise rotation of intestinal loop (90°) around the axis of sup.mesen.artery Cephalic limb moves downwards and to right and caudal limb to upwards and left © Dr.N.Mugunthan
- 34. Second Stage(5- 10week) Right limb grows rapidly and forms jejunal & ileal loops. Left limb – appearance of caecal diverticulum (caecum and appendix). Re-entry of herniated loop into abdomen ROTATION OF MIDGUT CONT… © Dr.N.Mugunthan
- 35. Second Stage cont…. Definitive order of reduction takes place. Right limb reduces first, passing posterior to the superior mesenteric artery occupies the central part of the abdomen. Left limb returns the last, caecum and midgut colon appears initially in left and then undergoes 1800 rotation to occupy the sub-hepatic region. ROTATION OF MIDGUT CONT… © Dr.N.Mugunthan
- 36. Second Stage cont…. Appearance of caecal diverticulum (6th week) Proximal part enlarges - caecum Distal part persist as narrow tube –appendix To reach the right iliac fossa- the caecum and appendix undergoes 2700 rotation. ROTATION OF MIDGUT CONT… © Dr.N.Mugunthan
- 37. Third stage Caecum and appendix grows caudally from subhepatic region – right iliac fossa. Ascending colon – portion of colon from right iliac fossa to sub-hepatic region Fixation Prearterial segment of dorsal mesentery – persist as mesentery. Postarterial segment of dorsal mesentery – persist as transverse mesocolon. ROTATION OF MIDGUT CONT… © Dr.N.Mugunthan
- 38. Omphalocele: Failure of intestines return to abdominal Covering of hernial sac is the epithelium of umbilical cord which is a derivative of the amnion The size of the hernia depends on its contents. Immediate surgical repair is required MIDGUT– DEVELOPMENTAL ANOMALIES © Dr.N.Mugunthan
- 39. Anomalies of vitellointestinal duct 1. Umbilical faecal fistula 2. Enterocystoma 3. Raspberry tumour 4. Ileal diverticulum 5. Meckel’s diverticulum MIDGUT– DEVELOPMENTAL ANOMALIES CONT… © Dr.N.Mugunthan
- 40. MECKEL’S DIVERTICULUM Most common anomalies of the digestive tract. Occurs in 2 % of people. 2 inch long. Attached to anti-mesenteric border about 2 feet proximal to ileo-caecal junction. 2 times more prevalent in males than females. © Dr.N.Mugunthan
- 41. The tip may be free or attached to umbilicus/ any abdominal viscera by fibrous band. Structurally, similar to ileum. Occasionally, oxyntic cells secreting HCL are found in mucous membrane and heterotopic pancreatic tissue in muscular coat. Complication Formation of peptic ulcer – perforation. Inflammation – peritonitis. Intestinal obstrucion. MECKEL’S DIVERTICULUM CONT… © Dr.N.Mugunthan
- 42. ERRORS OF ROTATION During second stage Non-rotation of midgut – umbilical ring is dilated and permits the umbilical hernia en masse. Mal-rotation (reverse rotation) – in this caecum enters first and rotates upward and to right behind the superior mesenteric artery. Transverse colon pass behind SMA & 3rd part of duodenum lies in front of the SMA vessel. During third stage Defect in fixation – caecum and appendix may occupysubhepatic, right lumbar or pelvic region © Dr.N.Mugunthan
- 43. DEVELOPMENT OF HIND GUT Pre-allantoic part Left one third of transverse colon Descending colon Sigmoid colon Post-allontoic part (endodermal cloaca) Rectum Upper part of anal canal Epithelium of urinary bladder Most part of urethra © Dr.N.Mugunthan
- 44. The dorsal mesentery of descending colon disappears The dorsal mesentery of the sigmoid colon is retained as sigmoid mesocolon DEVELOPMENT OF HIND GUT CONT… © Dr.N.Mugunthan
- 45. DEVELOPMENT OF RECTUM & ANAL CANAL Urorectal septum – • A wedge of mesenchyme divides the cloaca into dorsal and ventral parts • Dorsal part – primitive rectum (rectum and cranial part of the anal canal) • Ventral part – primitive urogenital sinus (bladder and urethra) © Dr.N.Mugunthan
- 46. 7th week -urorectal septum fuses with cloacal membrane Divide the cloacal membrane into urogenital membrane (front) and anal membrane (behind) Perineal body – line of fusion of urorectal septum &cloacal membrane DEVELOPMENT OF RECTUM & ANAL CANAL CONT… © Dr.N.Mugunthan
- 47. Position of anal membrane represented in adult by pectinate line DEVELOPMENT OF RECTUM & ANAL CANAL CONT… © Dr.N.Mugunthan
- 48. Rectum: Above the Houston’s 3rd valve (middle rectal valve) developed from - Preallantoic part Below the Houston’s 3rd valve developed from – dorsal part of endodermal cloaca DEVELOPMENT OF RECTUM & ANAL CANAL CONT… © Dr.N.Mugunthan
- 49. Anal canal: Above the pectinate line – from dorsal part of endodermal cloaca Below the pectinate line – from ectodermal proctodeum DEVELOPMENT OF RECTUM & ANAL CANAL CONT… © Dr.N.Mugunthan
- 50. DEVELOPMENTAL ANOMALIES OF HINDGUT Hirschsprung’s disease (congenital megacolon) Undivided cloaca Rectal fistula Recto-vesical fistula (high fistula) Recto-urethral or recto-vaginal fistula (low fistula) Imperforate anus Ectopic anus © Dr.N.Mugunthan
- 51. SUMMARY 1. Fore gut – prelaryngeal & postlaryngeal part 2. Mid gut – prearterial & postarterial segment 3. Hind gut – preallontoic & postallontaoic part Development of Foregut & its congenital anomalies Midgut & its congenital anomalies Hindgut & its congenital anomalies © Dr.N.Mugunthan