Embryology of GI tract Flashcards
What is the Liver bud an outgrowth from?
When does it appear?
Distal foregut
Appears in week 3
What is the septum transversum
Transverse partition between pericardial cavity and abdominal cavity
What happens to the connection between the liver bud and duodenum?
Narrows to bile duct
After 36 days what outgrows from the bile duct?
Gall bladder
What does mesoderm of the transversum septum form as the liver grows?
Greater omentum and falciform ligament
What are the two Ventral mesentries?
Lesser omentum- connects liver to stomach and duodenum
Falciform ligament- connects liver to anterior abdominal wall
When does the Stomach start to develop?
Week 4
What are the 5 Stages of the development of the Midgut?
Elongation
Physiological Herniation
Rotation
Retraction
Fixation
When does Physiological herniation occur? What happens?
Week 6
Protrusion into the umbilical cord
What happens during Elongation in the development of the Midgut?
Formation of the primary intestinal loop
Connection to yolk sak (Viletine duct) narrows
What three structures is the Cephalic limb of the Primary Intestinal loop made up from?
Distal part of Duodenum
Jejunum
Part of Ileum
What 5 structures make up the Caudal limb of the Primary Intestinal loop?
Distal part of Ileum
Caecum
Appendix
Ascending Colon
Proximal 2/3 of transverse colon
What does Herniate mean? What does the Intestinal loop herniate into? During which week?
Herniate- moves into
Umbilical Cord
6th week
Why does the Intestinal loop herniate into the umbilical cord?
Abdominal cavity too small for gut and liver
What Rotates during Stage 3 of the Development of the Midgut?
The caudal limb
What direction and how many degrees does the Caudal limb rotate?
Anticlockwise and 90 degrees
What do the Parts destined to be the small intestine develop during continued Elongation that the parts destined to be the large intestine do not?
Coils
What Week does the gut loop return to the abdomen?
Week 10
What does the gut do once it has re entered the abdominal cavity?
Rotates a further 180 degrees anticlockwise
What returns to the abdominal cavity first after retraction? What returns to the abdominal cavity second? Where does each structure settle?
Jejenum returns first
Ileum returns second
Jejenum settles towards left and Ileum settles towards right
What returns to the gut last during retraction? Where does it return to and where does it settle?
Caecum returns last to right upper quadrant
Descends and settles in Right iliac fossa
What happens during The fixation stage? What is the layer called that forms?
Parietal peritoneum on the posterior body wall and the visceral peritoneum on the organ join together forming a fascial layer called toldt fascia
What develops from the caecal bud as it descends from the upper right quadrant to the right iliac fossa?
Appendix
What three processes can congenital anomalies occur with?
Gut rotation
Return of gut loops to abdomen
Mesentries
What is Meckel’s diverticulum?
When the Vitelline duct forms an out-pouching from ileum (Congenital anomaly)
What is the condition called when the midgut loop doesn’t return to the abdomen?
Omphalocele
Gut is covered with amnion
What does the last part of the hindgut communicate with?
The cloaca
What is the Cloaca?
Cavity of the urogenital and anorectal in early embryos
What forms in the cloaca that separates the urogenital sinus from the cloaca?
Urorectal septum
How does the Lower anal pit form?
Invagination of the Ectoderm
What membrane ruptures allowing what two structures to become continuous with one and other?
Cloacal membrane ruptures
Allows upper and lower parts of anal canal to become continuous
