Embryo Flashcards
What are the major steps of the early genesis of the gut?
- Lateral folding of the body wall
- Diaphragm formation
- Cranio-caudal progression of apoptosis
- Foregut clockwise rotation and fixation
- Midgut umbilical herniation, cecum and appendix counter clockwise rotation
- Abdominal counter clockwise rotation
What happens during Foregut clockwise rotation and fixation?
- 90 degree clockwise rotation of the stomach
- The duodenum becomes retroperitoneal with the help of ligament of Treitz
- Pitx-2 (gene) expression in dorsal mesogastrium = critical point where situs inversus begins
- The right and left Vagus nerves become anterior and posterior after the rotation
- The liver grows in the right peritoneal space
- As the liver develops into the ventral mesentry, the mesothelium and supporting mesenchyme (omental bursa) will form 3 identifiable structures: lesser omentum, capsule of the liver and falciform ligament
- Then, the omental bursa expands caudally and forms the greater omentum within the mesogastrium
- Then, the formation of the lineo-renal and gastro-splenic ligaments will fix he foregut
What is the origin of the mesentery and its role in early morphogenesis of the gut?
- Growth in length of the gut and dorsal mesentery is accompanied by movement of the enlarging viscera in the available space
- The gut and vascular dorsal mesentery may be gradually displaced to the left side (or right side) against the coelomic-epithelial-lined posterior abdominal wall (degrees of fixation may occur)
- Then, there is a fixation from the medial origin to lateral free edge
- Primitive dorsal mesentry division:
- Mesoeosophagus
- Mesogastrium
- Mesoduodenum
- Mesentery proper
- Mesocolon
- Mesorectum
- Then, the continuous primitive dorsal mesentry specializes and the basic blood supply it formed: The Vitelline arteries fuse to form arterial trunks for foregut (coeliac artery), midgut (superior mesenteric artery) and hindgut (inferior mesenteric artery); variations can occur here
What are t2 important ligaments in the gut formation?
Mesoduodenum
- Superior retention band –> Ligament of Treitz very important role in rotation of the midgut and the fixation and the shape of the duodenu
Mesentery proper
- The Inferior Retention Band –> Phrenico-Colic Ligament forms the splenic flexure of the large intestine (hindgut)
What structures are formed in the foregut?
- Oesophagus
- Stomach
- Proximal half of duodenum
- Liver: pancreas
- Coeliac artery, nerve and ganglia
- Portal vein
- Splenic vein
- Gastric vein
What structures are formed in the midgut?
- Distal half of duodenum
- Jejunum + ileum
- Ascensing colong and ¾ of tranverse colon
- SMA, SMV, SMN, SMG
What structures are formed in the Hindgut?
- ¼ colon
- Sigmoid colon
- Rectum
- IMA, IMV, IMN, IMG
How is the portal vein system formed?
From the anastomotic channels between
2 vitelline veins
How is the pancreas formed?
- Common bile duct rotates with the ventral pancreatic bud
- Ventral pancreatic bud is positioned caudal to the dorsal bud with separate ducts
- Fusion of DPB and VPB and joining of ducts
PDx1 gene?
Important for the formation of insulin producing cells
Where do those anomalies come from?
Abnormality of lateral folding: diaphragmatic herniation, omphalocele (1), gastroschisis (2)
What’s that?
- Duodenal atresia: bilious vomiting at birth + polyhydramnios + double bubble sign in a CXR
Double bubble sign in a CXR can indicate what?
- Atresia of duodenum
- Annular pancreas
- Duodenal atresia
What is that?
Anterior duodenal portal vein variation: ANNULAR PANCREAS
When is Hox genes important?
During the midgut 180o counter clockwise rotation
–> Growth in length and differential growth of the cecum and appendix
What is that?
Meckel’s diverticulum
It is a midgut Development obliteration of Yolk Sac Remnants
What’s that?
Malrotation of midgut seen in newborn
What is that?
Organoaxial
Non-bilious vomiting
Whats is that?
Organomesenteric
Gastric ischemia
