Embyology Flashcards
What structure is folded to form gut tube?
Yolk sac is folded inwards and sealed from all ends to form the gut tube
What structure seals the cranial end of the gut tube?
The buccopharyngeal space
What structure seals the caudal end of the gut tube (rectum)
The cloacal membrane
What is the origin of the peritoneal cavity?
The intraembryonic coelom
Why is there a process of recanalization of the gut tube?
What are some of the outcomes when this process goes wrong?
Recanalization is necessary because proliferation exceeds lengthening of the gut tube– it becomes occluded, and needs to be hollowed out.
Errors in recanalization lead to duplication, stenosis and atresia
What are the four divisions of the gut tube defined by?
Their blood supply
What is the source of blood supply for each regional division?
Thoracic foregut: aortic arches
Abdominal foregut: celiac artery
Midgut: SMA
Hindgut: IMA
Name three anomalies of the esophagus and describe them.
Esophageal atresia and stenosis– blockage/narrowing of esophagus
Tracheoesophageal fistula: displacement of septum between trachea and esophagus results in incomplete separation of respiratory/esophageal tubes
Congenital hiatal hernia: Esophagus doesn’t elongate properly, displacing part of stomachh into thoracic cavity
Which wall grows more rapidly: dorsal or ventral? What are implications?
The dorsal wall grows more rapidly, forming the greater (dorsal) and lesser (ventral) curvature of the stomach
What is the fate of the dorsal and ventral mesentery? What structure connects them?
The dorsal mesentery expands to become the greater momentum
The ventral mesentery expands to become the lesser momentum
The epiploic foramen connects the two compartments
Describe the process of liver formation
Hepatic plate proliferation forms the hepatic diverticulum, which grows into the ventral mesentery
The hepatic diverticulum gives rise to hepatic cords, duct and bile clinical
Ventral mesentery connects liver to stomach (lesser omentum) and ventral body wall (falciform ligament)
What does the cystic diverticulum form?
Gallbladder and cystic duct
What is gallbladder duplication?
Splitting of the cystic diverticulum that is usually asymptomatic
What is extra hepatic biliary atresia?
Obstruction of the bile duct due to a failure to canalize
Describe the process of pancreas formation:
Dorsal pancreatic bud forms on dorsal duodenum, and grows into dorsal mesentery
Ventral pancreatic bud forms on ventral duodenum (caudal to hepatic/cystic diverticuli) and grows into ventral mesentery.
They fuse during weeks 5-6 and the dorsal pancreatic duct degenerates
What is angular pancreas?
Two attached ventral buds rotate in opposite directions to fuse with dorsal bud causing duodenal stenosis or atresia
Describe midgut formation:
Elongation, rotation, retraction and second rotation
What is congenital omphalocele?
Herniation of the intestines into the umbilical cord due to a failure of the midgut to return to the abdomen at week 10
What is an umbilical hernia?
Failure of the umbilicus to close completely results in intestinal herniation following appropriate return to the abdomen
What is gastroschisis?
Extrusion of might structures through the ventral body wall due to incomplete lateral folding during week 4
What is Meckel’s diverticulum?
A remnant of the yolk stalk persists as an outpouching of the ileum– it may contain gastric/pancreatic tissue and can appendicitis-like symptoms
What are two defects of midgut rotation and fixation?
Non-rotation and Volvulus
Hirschsprung’s disease
Dilation of colon due to peristalsis defect— failure of neural crest migration and enteric ganglion formation
Membraneous atresia
Failure of anal perforation during week 8
