Development Of Gut (3) Flashcards
What does the midgut develop into?
Duodenum
Jejunum
Ileum
Caecum
Ascending colon
2/3s of transverse colon
What week of development does the midgut undergo rapid elongation?
6th week
What other viscera develops at the same time as the rapid elongation of the midgut?
Liver
There is limited space in the abdominal cavity as the midgut (intestinal loop) and liver develop, how does the body compensate for the lack of space in the abdominal cavity?
Intestinal loop herniates through the umbilical cord
What blood vessel acts as an axis of rotation for the intestinal loop?
Where is the small intestine and large intestine positioned in relation to the SMA before rotation?
Superior mesenteric artery
Small intestine above
Large intestine below
How does the intestinal loop first rotate around the superior mesenteric artery?
What position does this put the small intestine and large intestine in?
90 degree anti-clockwise rotation
Small intestine on RHS and Large intestine on LHS. (L for Large + L for Left)
After the first 90 degree anti-clockwise rotation of the intestinal loop, how does it then rotate?
What position does this leave the intestines in?
Does 2 more 90 degree counter clockwise rotations
Small intestine to the left of the large intestine
What part of the large intestine moves between the 2nd and 3rd rotation of the intestinal loop?
Where does it end up?
Caecum descends
Moving from near the liver to its normal spot in the right iliac fossa
When does the physiological return of the midgut herniation back to the abdominal cavity occur?
10th week of development
How many 90 degree anti-clockwise rotations does the midgut (intestinal loop) do in normal development?
3 rotations
What is a complication if the midgut only does 1 90 degree anti-clockwise rotation instead of 3?
Colon is left sided (left iliac fossa instead of right)
What happens if the intestinal loop/midgut only does 1 90 degree rotation but in the clockwise direction?
Transverse colon will be posterior to the small intestine instead of the normal anterior
What is omphalocele?
When midgut herniation fails to return to the abdominal cavity at the 10th week of development
How does omphalocele present?
The herniated contents of the midgut are covered by peritoneum so are not exposed to amniotic fluid
What is Gastroschisis?
Where the abdominal wall fails to form allowing the abdominal viscera to herniate through the defect
How do the herniated contents differ in Omphalocele and Gastroschisis?
Midgut contents covered with peritoneum in Omphalocele
Midgut contents in Gastroschisis not covered by peritoneum so are exposed to the amniotic fluid
What has the higher mortality rate and why, Omphalocele or Gastroschisis?
Omphalocele = higher mortality rate
Omphalocele associated with more genetic abnormalities
What is the Vitelline duct?
Connection between the midgut structures and the yolk sac
When does the Vitelline duct normally regress?
7th week of development
What are 3 potential Vitelline duct abnormalities?
Vitelline cyst
Vitelline fistula
Meckels diverticulum
What is a Vitelline cyst?
When the Vitelline duct fails to fully regress leaving a patent middle section of the duct
What is a Vitelline fistula?
Where there is still a complete connection between the midgut and umbilicus (Vitelline duct hasn’t regressed at all)
Can get faecal discharge from umbilicus
What is Meckels diverticulum?
A small out-pouching of the small intestine (like an appendix off the small intestine)
Most common abnormality
What complications can occur if the recanalisation of the midgut lumen is incomplete?
Atresia = absence of lumen
Stenosis = narrowing of the lumen
Mainly affects the duodenum
How are the small intestine and large intestine positioned relative to the superior mesenteric artery before rotation takes place? (look at slide 5)
Small intestine superior
SMA
Larger intestine inferior
