RCSI Embryology of Gut Tube 2 PDF 2024

Embryology of Gut tube 2 Class Year 2, Semester 1 Lecturer Fiona Cronin Department of Anatomy [email protected] Date 08-10-2024 1  Learning outcomes Describe the normal development of the liver, biliar...

Embryology of Gut tube 2 Class Year 2, Semester 1 Lecturer Fiona Cronin Department of Anatomy [email protected] Date 08-10-2024 1  Learning outcomes Describe the normal development of the liver, biliary tree and pancreas Discuss the haemopoietic function of the liver in the embryo Describe the main biliary and pancreatic congenital (developmental) abnormalities and how they present in neonates Explain the normal development of the midgut, including physiological herniation and rotation Discuss the main congenital abnormalities that may occur with midgut development and how they present in neonates Describe the role of the vitelline duct in midgut development and how it may abnormally persist and pathologically present in the neonate or adult Identify the blood supplies to the foregut and midgut LIVER & PANCREAS http://staff.um.edu.mt/acus1/Gastro-intestinal.pdf http://staff.um.edu.mt/acus1/Gastro-intestinal.pdf http://staff.um.edu.mt/acus1/Gastro-intestinal.pdf  Mesoderm on the surface of the liver differentiates into visceral peritoneum except the cranial surface The portion of the septum in contact at the cranial surface of liver will form the central tendon of diaphragm The surface of the liver that is in contact with the future diaphragm is never covered by peritoneum which forms the bare area of liver  Liver development Liver is large 10th week – is around 10% of body weight At birth – is 5% of body weight Functions: Haematopoiesis begins approximately 6 weeks after fertilisation Major site of pre-natal haematopoiesis Bile formation begins around week 12 This diagram illustrates the time scale and relative importance of the various sites where HAEMOPOIESIS occurs in embryonic and fetal life  Gallbladder and biliary tract Caudal offshoot from liver bud Forms the gallbladder & cystic duct The connection between the liver bud & foregut narrows Forms common bile duct (CBD) Lumen obliterates, then recanalises (just like the duodenum) CBD originally ventral to duodenum Stomach rotates & mesenteries move… Liver moves right, and duct moves behind duodenum to enter from left side  Clinical correlates Accessory hepatic ducts Duplication of gall bladder Biliary atresia  Pancreas Initially forms as 2 separate endothelial buds from foregut Dorsal bud (at end of foregut) appears at start of 4th week Ventral bud appears a few days later, from the liver bud http://staff.um.edu.mt/acus1/Gastro-intestinal.pdf http://staff.um.edu.mt/acus1/Gastro-intestinal.pdf http://staff.um.edu.mt/acus1/Gastro-intestinal.pdf Proximal part of the dorsal pancreatic duct either is obliterated or persists as accessory pancreatic duct The main pancreatic duct is–formed by the distal part of the dorsal pancreatic duct & entire ventral pancreatic duct http://staff.um.edu.mt/acus1/Gastro-intestinal.pdf  Annular Pancreas 1/20,000 Bilobed (split) ventral pancreatic bud One half moves anterior, the other posterior to the duodenum → surround duodenum, constricting it Symptoms depend on degree of stricture (vomitting, non-bilious > bilious) May have other congenital / neonatal conditions MIDGUT  Clinical Vignette An infant was born with a light gray, shiny mass measuring the size of an orange and protruding from the umbilical region. It was covered with a thin transparent membrane  Midgut Dorsal aorta with the 3 branches for the GIT Pharyngeal gut: buccal membrane → respiratory diverticle (mouth cavity - head and neck). Foregut: up to the hepatic Pharyngeal gut bud: oesophagus – Respiratory bud stomach – first half of duodenum – liver and FOREGUT pancreas. → Territory of coeliac trunk Septum transversum Midgut: up to the left third of the transverse colon MIDGUT → Territory of superior mesenteric artery Hindgut: up to the cloaca → Territory of inferior mesenteric artery HINDGUT Cloacal membrane Cloaca Midgut Coeliac trunk - foregut Supplies foregut & foregut derivatives From lower oesophagus to major duodenal papilla Stomach, spleen, liver, gallbladder Most of pancreas & duodenum Superior mesenteric artery - midgut From major duodenal papilla to proximal 2/3 of transverse colon Inferior pancreaticoduodenal branch also supplies duodenum & pancreas Inferior mesenteric artery - hindgut Splenic flexure to upper anal canal  Superior mesenteric artery Let’s refresh: distal duodenum- jejunum- ileum- caecum - appendix - ascending colon - transverse colon near splenic flexure http://staff.um.edu.mt/acus1/Gastro-intestinal.pdf  Midgut derivatives Proximal 2/3rd of http://staff.um.edu.mt/acus1/Gastro-intestinal.pdf transverse colon http://staff.um.edu.mt/acus1/Gastro-intestinal.pdf http://staff.um.edu.mt/acus1/Gastro-intestinal.pdf http://staff.um.edu.mt/acus1/Gastro-intestinal.pdf http://staff.um.edu.mt/acus1/Gastro-intestinal.pdf  Clinical correlates Body wall defects Omphalocele Gastroschisis  Clinical correlates Vitelline duct abnormalities Enterocystoma/Vitelline cyst Meckel’s/Ileal diverticulum Vitelline fistula  An inflamed Meckel’s Diverticulum can be misdiagnosed as appendicitis Like the stomach, MECKEL’S DIVERTICULUM obeys the “Rule of 2”. It occurs in 2% of people, is situated 2 feet from the ileocaecal junction, is usually 2 inches long, 2 times more common in boys, and the peak age for symptoms is 2 years. It normally contains the typical lining of the small intestine but 2 types of abnormal lining can be present: ectopic gastric mucosa (acid-producing) and ectopic pancreatic exocrine tissue. Most examples of a Meckel’s Diverticulum are lined with the normal lining of the small intestine, but sometimes ectopic gastric mucosa is present and this can be associated with the formation of a peptic ulcer there. This specimen has a well-differentiated tumour of neurendocrine cells growing at its tip. This is the most common type of tumour associated with Meckel’s Diverticulum.  Clinical correlates Gut rotation defects Volvulus Non-rotation & Reverse rotation References Acknowledgement Prof. Robin Prof. Fabio Quondamatteo