2023 Embryology Lecture - GIT PDF

ORISH CHINNA ,UNIPORT ,2023 EMBRYOLOGY GIT(ENDODERMAL ORIGIN} DIAGRAM GIT SUBDIVISION OF GIT ▪ PHARYNGEAL GUT(from buccopharyngeal membrane to the tracheobronchial diverticulum) ▪ FOREGUT ▪ MIDGUT ▪ HINDGUT FOREGUT(Coeliac A) ▪ Lung buds ▪ Oesophagus ▪ Stomach ▪ Pancreas ▪ Li...

ORISH CHINNA ,UNIPORT ,2023 EMBRYOLOGY GIT(ENDODERMAL ORIGIN} DIAGRAM GIT SUBDIVISION OF GIT ▪ PHARYNGEAL GUT(from buccopharyngeal membrane to the tracheobronchial diverticulum) ▪ FOREGUT ▪ MIDGUT ▪ HINDGUT FOREGUT(Coeliac A) ▪ Lung buds ▪ Oesophagus ▪ Stomach ▪ Pancreas ▪ Liver& extrahepatic biliary system ▪ Proximal part of duod to d entrance of bile duct MIDGUT(Superior mesenteric A) ▪ Duod. distal to entrance of bile ▪ Ascending colon ▪ Jejenum ▪ Ileum ▪ Caecum ▪ Appendix ▪ Right 2/3 & left 3rd of transverse colon(proximal portion). HIND GUT(Inferior mesenteric A) ▪ Distal 3rd or left 3rd of transverse colon(distal) to upper part of anal canal(cloacal membrane) ▪ Transverse colon ▪ Descending colon ▪ Sigmoid ▪ Rectum ▪ Upper part of anal canal ESOPHAGUS ▪ 4th WK ▪ Appearance of resp diverticulum(lung bud) at ventral wall of foregut ▪ Esophagotrachael septum ▪ Partions resp. Diverticulum ▪ into ▪ Dorsal portion(Esophagus), Ventral portion ESOPHAGUS DEVPT.CONTD ▪ Dorsal portion{esophagus} ▪ At 1st is short Lengthens rapidly w descent of heart & lung ▪ Has ▪ Muscular coat ▪ ▪ Upper 2/3( striated); Lower 1/3(smooth mms) Innervated by vagus; ;By splanchnic plexus DIAGRAM DUODENUM ▪ Terminal part of the foregut +Cephalic part of midgut ▪ Rotation of the stomach result in ▪ C- shaped duo. that rotates to the R ▪ F FFurther rotation & growth of pancreatic head ▪ Moves duod. From its initial midline position to the r side of the abdominal cavity. ▪ STOMACH ▪ 4th WK ▪ Fusiform dilation of foregut ▪ 2 Rotations in the course of devpt Anteropost.axis & 900clockwise ard its longt axis ▪ ▪ Forms ▪ Pyloric part Cardiac part ▪ Moves to the R upward Moves to the left down  900 CLOCKWISE AROUND THE LONGTIDUNAL AXIS ▪ {L}side to face ant { R} side to face post. ▪ Innervated by Innervated by ▪ {L} vagus moves ant. { R} vagus mov post ▪ Faster growth of post wall than ant ▪ Result in ▪ Greater curvature & Lesser curvature ▪ ▪ STOMACH ▪ Stomach appears first as a fusiform dilation of the foregut endoderm which undergoes a 90° rotation such that the left side moves ventrally and the right side moves dorsally (the vagus nerves follow this rotation which is how the left vagus becomes anterior and the right vagus becomes posterior). ▪ Differential growth establishes the greater and lesser curvatures; cranio-caudal rotation tips the pylorus superiorly ▪ Dorsal AND ventral mesenteries of the stomach are retained to become the greater and lesser omenta, respectively ▪ Lesser omentum: The lesser omentum is a smaller fold of peritoneum that connects the liver to the lesser curvature of the stomach and the beginning of the duodenum. It helps to suspend and support the liver and contains structures such as the common bile duct and the hepatic artery. R(post) Left(ant) STOMACH ATTACHMENT ▪ STOMACH ▪ Is attached to Ventral wall Dorsal wall by by Ventral mesogastrium Dorsal mesogastrium Forms Forms Lesser omentum & Gastrosplenic lig.& Falciform ligament Lienorenal lig. LESSER OMENTUM(connects liver & stomach) FREE MARGINLesser omentum Its free margin Hepatoduod.lig. Epiploic foramen of Winslow Contains Contains Portal triad Omental bursa & ( bile duct, Peritoneal cavity Portal vein & hepatic artery) FALCIFORM LIGAMENT(connects liver & abd. Wall) FREE MARGIN Falciform ligament Its free margin contains Umblical vein Oblitrates after birth Round ligament of the liver(ligamentum teres hepatis) LIVER &GALL BLADDER ▪ 3rd WK ▪ Outgrowth of endodermal epithelium at distal end of foregut To form ▪ Liver bud/diverticulum Via mesogastrium ▪ Penetrates septum transversum And divides into LIVER & GALL BLADDER DEVT CONTD ▪ Pars cystica Pars hepatica Forms Forms ▪ Gall bladder Liver ▪ Note that parts of the bud proximal to its division forms the bile duct DIAGRAM PANCREAS From endodermal lining of duodenum 2 buds originate Dorsal pancreatic duct Ventral pancreatic duct ( in dorsal mesentry) Rotation of duod. to the R to become C- shaped Ventral pancreatic duct moves dorsally to lie below dorsal pancreatic duct PANCREAS DEVPT CONTD. Ventral panreatic duct Forms Uncinate process ,Inferior part of the head of pancreas ▪ Note that the proximal part of pancreatic duct obliterates or persists as small channel (Accessory pancreatic duct of Santorini) ▪ Main pancreatic duct = proximal ventral pancreatic duct + distal dorsal pancreatic DIAGRAM DIAGRAM  Rotation of the duodenum brings the ventral and dorsal pancreas together Larsen’s fig 14- 09 Aberrations in this process may result in an annular pancreas, which can constrict the duodenum. Also, since the dorsal and ventral pancreas arise by different mechanisms, it’s possible that one or the other may be absent in the adult. Larsen’s fig 14- MIDGUT ▪ Rapid elongation of the gut and its mesentry ▪ Forms primary intestinal loop ▪ Cephalic limb ; Caudal limb ▪ 1.Distal part of duod. 1. Lower portion of ileum ▪ 2.Jejenum 2. Cecum ▪ 3.Upper part of ileum 3. Appendix ▪ 4. Ascending colon ▪ 5. Proximal 2/3 of transverse colon MID GUT DEVT CONTD. As a result of rapid growth of intestinal loop or expansion of liver Abdominal cavity becomes too small contain intestinal loop Intestinal loops enters extraembryonic cavity via umblical cord (physiological herniation) MID GUT DEVPT CONTD. ▪ Also in the course of rapid growth ▪ Counter clockwise rotation takes place ▪ (2700) ▪ 900 1800 During herniation Return of intestinal ▪ loop into abdominal cavity  6 weeks Rotation of midgut loop - Counterclo ck wise 90 10 weeks Retum of midgut to abdomen 11 weeks THANKS FOR LISTENING