s3. development of the gut 3 and 4 Flashcards
midgut consists of
2nd part duodenum jejunum illeum caecum ascending colon 2/3rd transverse colon
describe herniation of the midgut. what week does this occur?
intestinal loop elongates rapidly
at the same time liver is developing> not enough room for both viscera to develop
therefore> intestinal loop herniates out umbilical cord to give space
occurs in week 6
which artery runs through the intestinal loop
superior mesenteric artery
SMA
when does the intestinal loop return to the abdominal cavity?
week 10
describe development problems with the midgut
Malrotation
1x 90° rotation
> results in L sided colon
Reversed rotation
1x 90° rotation clockwise (instead of ANTI clockwise)
> results in transverse colon behind S. intestine.
normal position of midgut
after 270° rotation
transverse colon in front of S. intestine.
lateral folding forms what
pathology?
forms anterior abdominal wall normally
if lateral folding incomplete, abdominal wall fails to form anteriorly so abdominal viscera herniates > GASTROSHISIS.
vitelline duct abnormalities: what is vitelline cyst?
patent middle section of the duct
vitelline duct abnormalities: what is vitelline fistula?
when the connection between midgut and developing yolk sac remains completely intact
> at birth the connection between midgut and umbilicus> see faecal contents through umbilicus
what is the most common vietelline duct abnormality?
Meckels diverticulum 2% of population located 2 feet proximal to ileo-caecal valve detected in under 2s 2:1 ratio M:F
what does atresia mean?
no lumen
result of unsuccessful recanalisation > often affects duodenum
can also have partial recanalisation which leads to stenosis (narrowed lumen)
hindgut consists of
distal 1/3 transverse colon descending colon sigmoid colon rectum superior anal canal bladder epithelia
what is the cloaca?
terminal end of hind gut
what is the function of the urorectal septum in the 4th-7th week?
descends and separates cloaca into urogenital sinus an anorectal canal
what is the pectinate line?
junction of ectoderm and endoderm at anus
also called dentate
