Embryology Development & Congenital anomalies of the GI tract Flashcards
What are the derivatives of the foregut?
Oesophagus Trachea and lung buds stomach Duodenum proximal to entrance of bible duct Liver, biliary apparatus and pancreas
What are the derivatives of the midgut?
Duodenum distal to opening of bile duct
Small intestine
Caecum and appendix
Ascending colon and 2/3rds of transverse
What are the derivatives of the hindgut?
Distal 3rd of transverse colon, descending colon, sigmoid colon
Rectum and superior part of anal canal
Epithelium of bladder & most of urethra
What is the arterial supply to the foregut?
Coeliac trunk
What is the arterial supply to the midgut?
SMA
What is the arterial supply to the hindgut?
IMA
Describe the characteristics of the oesophageal muscle, upper 2 res vs lower 1 third
Upper 2/3: Striated muscle innervated by vagus nerve
Lower 1/3: Smooth muscle innervated by splanchnic plexus
Describe the rotation of the stomach.
Turns 90 degrees on the longitdinal axis so left side is anterior and right posterior
AP rotation, caudal part moves right and upward
Where is the lesser omentum
between lesser curve of stomach and liver
Where is the falciform ligament
liver to ventral wall of abdominal wall
At what week does haematopoiesis begin giving the liver its read appearance
week 6
At what week does bile formation start?
Week 12 → dark green bowel contents
Briefly describe the embryology of the pancreas.
Th larger dorsal pancreatic bud develops 1st, a ventral pancreatic pub develops near the entry of the bille duct.
The dorsal pud is a accessory duct to the duodenum (minor papilla) and the ventral bud has the main pancreatic duct (major papilla)
As the duodenum rotates the two buds form and the main duct remains patent whilst the accessory duct closes. This fails to close in 10%.
When does insulin secretion start?
Month 5 - islets of langerhan
Why does physiological herniation of the midgut occur?
As the midget elegonates rapidly as does the size of the liver, there is not enough space within the developing abdominal cavity, therefore at week 6 the loops entry the extra embryonic cavity in the umbilical cord → physiological herniation
It renters at week 10.
Which is the last part of the gut to reenter the abdominal cavity
Caecum
Then descends in LIF, as descends appendix produced as a diverticulum
What structures are retroperiteonal (anterior side has peritoneum)
Duodenum (except fist 2.5cm)
Ascending colon
Descending colon
What structures retain their free mesenteries
Jejenum and ileum
Lower and of caecum and appendix
Transverse colon (fuses with posterior wall o f greater omentum)
Sigmoid colon
Describe the connection of the urogenital system and hindgut at week 5
The allantois (future urogenital sinus) and hindgut unite at the cloaca (all endoderm) which comes into contact with the surface ectoderm at the cloacal membrane.
An area of mesodermal tissue between the allantois and hindgut→ the urorectal septum
How does the allantois/hingut/urorectal change as the future develops
The urorectal septum moves closer to the cloacal memabrane/
At week 7 the cloacal membrane breaks down which creates an opening of the anal canal and a ventral opening for the urogenital sinus. The tip of the urorectal septum forms the perineal body.
Proliferation of the ectoderm → proctodeum the lowest region of the anal canal
Describe the embryological orgins of the anal canal
Superior 2/3 endoderm of the hindgut
Inferior 1/3 ectoderm of proctoderm
Junction pectinate late, just below anal columns
Arterial supply of superior 2/3rds of anal canal
Superior rectal artery (cont. of IMA)
Arterial supply of inferior 1/3rd of anal canal
Inferior rectal artery (branch of internal pudendal artery)
Venous drainage of superior 2/3rds of anal canal
Superior renal vain (inferior mesenteric vein)
