EMBRIOLOGYof

DIGESTIVE SYSTEM

By Rita Rosita

Divisions of Gut Tube

Result of cephalocaudal and lateral folding Primitive Gut : – Pharyngeal gut : bucopharyngeal mbr – tracheobr

diverticulum– Foregut : caudal pharyngeal tube- liver bud– Midgut :liver bud – 2/3 prox colon transversum– Hindgut : 1/3 distal colon transv – cloacal mbr

Foregut

ESOPHAGUS• 4 weeks old : lung bud appears from ventral

wall of the foregut tracheoesophageal septum :– Respiratory primordium : ventral– Esophagus : dorsal

Clinical Correlates

• Esophageal atresia

• Tracheo-esophageal fistula

• Congenital hiatal hernia

STOMACH• 4th week :fusiform dilatation• Rotate :longitudinal and anteroposterior axis

Foregut

Mesentery• Stomach attached to :– Dorsal dorsal mesogastrium– Ventral : ventral mesogastrium

• Rotation longitudinal axis : space behind stomach bursa omentalis, lengthen of dorsalmesogastrium : spleen and pancreas become retroperitoneal

• Rotation ant-post axis : omentum majus

Duodenum• As the stomach rotates C-shaped , swings to

the left side of abdominal cavity• Duodenum and pancreas dorsal body wall

retropertoneal, except duodenal cap• 2nd month, lumen of duodenum obliterated

recanalisation

Foregut

Liver and Gall Bladder

• 3rd week : outgrowth endodermal epithelium at distal part of foregut liver bud penetrate septum transversum

• Connection between liver bud and duodenum narrowing bile duct , gall bladder, cystic duct

• 10th week ; the liver approximately 10% of total body weight 5% at 7th month

Clinical Correlates

• Duplication of gall bladder• Extrahepatic biliary atresia

Pancreas• Formed by two buds originating from endodermal

lining of duodenum– Dorsal pancreatic bud– Ventral pancreatic bud

• Duodenum rotates ventral pancreatic bud comes to below and behind the dorsal bud

• Ductus pancreaticus major (Wirsungi) : formed by distal part of dorsal pancreatic duct and entire ventral pancr duct

• Ductus pancreaticus minor (Santorini) : proximal part of dorsal pancr duct

Pancreatic abnormalities

• Annular pancreas• Accessory pancreatic tissue

Midgut

• 5th week : midgut suspended :– Dorsal : dorsal mesentery– Ventral : communicates with the yolksac by

vitteline duct• Rapid elongation of gut and its mesentery

primary intestinal loop– Cephalic limb : distalpart duodenum, jejunum,

part of ileum– Caudal limb: lower part of ileum, caecum,

appendix, ascending colon, 2/3 prox colon

• Physiological herniation ; as a result of rapid elongation and expansion of the liver, during 6th week

• Rotation of the midgut : primary intestinal loop rotates around an axis formed by superior mesenteric artery, counterclockwise, 270°.

• Coiling phenomenone : cephalic limb• Retraction of herniated loop : during 10th week,

jejunum is the first part which reenter the abdominal cavity, lie on the left side, cecal bud is the last

Midgut Abnormalities

• Omphalocele : herniation of abdominal viscera through enlarge umbilical ring

• Gastroschisis : herniation of abdominal content through abd wall directly into amniotic cavity.

• Vitteline duct abN : persistens, cyst, fistula• Gut rotation deffect• Gut atresias/stenosis

Hindgut

• The terminal portion : the primitive anorectal canal

• Cloaca covered by surface ectoderm,the boundary :cloacal membrane

• Urorectal septum: separates allantois-hindgut, come closer of cloaca membrane

• 7th week :Cloaca mbr ruptures :– Ventral opening : urogenital sinus– Dorsal opening : hindgut

•The tip of urorectal septum form the perineal body•Proliferation of ectoderm closes the caudalmost region of the anal canal •Recanalization during 9th week

Hindgut Abnormalities• Rectoanal atresia and fistula• Imperforate anus