Development 2 Flashcards
What does teh midgut give rise to (twisting - can lead to duodenal obstructing, compression fo blood supple, ishacemia)
• Gives rise to: – Small intestine, including most of duodenum – Caecum & appendix – Ascending colon – Proximal 2/3 transverse colon
What happens to the primary intestinal loop
• The midgut elongates enormously • Runs out of space – Makes a loop that • has the SMA as its axis • is connected to the yolk sac by the vitelline duct (part of same tube) • has cranial & caudal limbs
What happens to the intestinal loop in the 6th week
• During 6th week, growth of the primary intestinal loop is very rapid
– elongation
• Liver is also growing rapidly
– abdominal cavity is too small to accommodate both
• Intestines herniate into the umbilical cord
Give an overview of midgut rotation
3x 90 degree turns
Continuing extension in length of small intestine
Cranial alove, then 90 turn, now Uber’s lie side by side. Another turn, and caudal limb at head end. As it returns to the cavity, another 90 degree turn
This meas that
cranial limb returns to abdominal cavity first, moving to the left side
Crackle bud grows. This grows down to create caecum and ascending colon
See slide
Give 2 examples of malrotation
• Incomplete rotation
– Midgut loop makes only one
90° rotation
• Left-sided colon bc caudal limb went back in first
• Reversed rotation – Midgut loop makes one 90° rotation clockwise • Transverse colon passes posterior to the duodenum
What are the risks associated with midgut defects
• Most complications present in the neonatal period
• Volvulus
– Strangulation, compression of blood supply,
– Ischaemia
What is volvulus
(twisting - can lead to duodenal obstructing, compression fo blood supple, ishacemia)
Describes some abnormalities in terms fo remnants of the yolk stalk
The vitelline duct can persist resulting a number of different abnormalities
vitelline cyst - Vitelline duct forms fibrous strands - fluid filled cyst in a fibrous cord
Vitelline fistula - Not lost the intel line duct - havent resolved communication between midgut and umbillicus - direct communication between them
meckels diverticulitis - remnant of yolk stalk - AKA ileal diverticulum, the most common GI anomaly
What is meckels diverticulum
AKA ileal diverticulum, the most common GI anomaly
• Rule of 2s
• 2% population
• 2 feet from ileocaecal valve
• Usually detected in under 2s
• 2:1 ration male:female
• Can contain ectopic gastric or pancreatic tissue
Why does recanlisation occur and where
• The primitive gut is a simple tube
• In some gut structures, cell growth becomes so rapid that the lumen is
partially or completely obliterated
– oesophagus, bile duct, small intestine • Recanalisation occurs to restore the lumen
• If recanalisation is wholly or partially unsuccessful, atresia or stenosis of the
structure can occur
What are atresia and stenosis
• Atresia
– Lumen obliterated
• Stenosis
– Lumen narrowed - limit passage but not completely blocked
• Most occur in duodenum
– Most likely cause is incomplete canalisation
– But “vascular accidents” may also contribute eg olvulus etc
What is pyloric stenosis
• Pyloric stenosis – hypertrophy of the circular smooth muscle in the region of the pyloric sphincter – NOT a recanalisation failure • Common abnormality of the stomach in infants – narrowing of the exit from the stomach causes characteristic projectile vomiting
What is gastrochisis
• Failure of closure of the abdominal wall during folding of the embryo • Leaves gut tube & derivatives outside the body cavitiy Relatively easy to correct
What is omplalocoele
• a.k.a. exomphalos
– Persistence of physiological herniation
– Differs from umbilical hernia because hernias have covering of skin and subcut. tissue
– i.e. in hernia, gut had completed physiological herniation sequence, but omphalocoele doesnt - major fundamental problem with development
Problem with development - has a spectrum of other structural defects
Wha does the hindgutgive rise to
• Gives rise to – Distal 1/3 transverse colon – Descending colon – Rectum – Superior part of anal canal – Epithelium of urinary bladder
