Development of midgut and hindgut Flashcards
What week does the development of the midgut start?
week 5
What happens in week 5?
Midgut and undergoes rapid elongation to form primary intestinal loop.
What two limbs does the primary intestinal loop have?
Cranial and caudal limbs
What happens in week 6?
More rapid elongation - not enough room in the abdomen, so primary intestinal loop herniates into the umbilical cord.
What rotation takes place as herniation occurs?
The midgut rotates 90 degrees anti-clockwise bringing the cranial limb to the right and caudal limb to the left.
What happens in week 10?
The midgut returns to the abdomen, and totates 180 degrees anti-clockwise. Bringing the proximal jejunal loops to the left side.
Where does the caecum lie in week 10?
Below the liver
What happens to the vitilline duct?
becomes obliterated ( destroyed)
What happens to the ascending and descending colon?
Dorsal mesentery shortens, they become secondarily retroperitoneal
What is Meckel’s diverticulum?
Remnant of the vitelline duct - creates an out-pocketing of the ileal wall
What is omphalocele?
Failure of midgut to return to abdomen in week 10. Viscera herniates into the base of the umbilicus.
What is volvulus?
Twisting of the midgut because dorsal mesentery remains intact and suspends organs that would normally be retroperitoneal such as the duodenum.
During the formation of the hindgut, where does the distal end of the hindgut enter?
Dorsal part of the cloaca
What is imperforate anus?
No anal opening because anal membrane fails to degenerate
What is hirchsprung disease// congenital anganglionic megacolon?
No innervation - failure of neural crest cells to migrate to the bowel - no peristalsis
What is the enteric nervous system derived from?
neural crest cells
