GI development Flashcards
at what point is organogenesis complete?
12 weeks
which organs are formed at what points of development?
- 4 weeks – gut tube forms
- 5 weeks – liver and pancreas formation
- 6 weeks – ventral pancreatic bud fuses with dorsal bud
- 7 weeks – primary intestinal loop herniates into the umbilicus and rotates
- 11 weeks – midgut rotates and retracts into abdomen
- 12 weeks – ascending and descending colon attach to body wall
what supplies the foregut, midgut and hindgut?
- Foregut supplied by the coeliac artery
- Midgut supplied by the superior mesenteric artery
- Hindgut supplied by the inferior mesenteric artery
what does the foregut give rise to?
pharynx, oesophagus, stomach, cranial half of the duodenum and the ampulla of Vater, liver parenchyma and hepatic duct epithelium, gallbladder, cystic duct and common bile duct
what does the midgut give rise to?
caudal half of duodenum, jejenum, ileum, cecum, appendix, ascending colon and proximal 2/3 of transverse colon
what does the hindgut give rise to?
distal 1/3 of transverse colon, descending colon, rectum and urogenital sinus
name foregut development abnormalities?
- Oesophageal atresia/stenosis – blockage
- Tracheo-oesophageal fistulae
- Congenital hiatus hernia
- Pyloric stenosis
- Duodenal atresia
what does failure to separate the oesophagus and respiratory tract lead to?
- Failure of separation
- Atresia of the oesophagus
- Atresia of the oesophagus with fistula
what can cause reflux in infants?
overfeeding
GORD
what can cause GORD in babies?
o Immaturity of motor function in neonates
o Suck reflex not present prior to 32 weeks’ gestation
o Lower oesophageal sphincter pressure is reduced
o Gastric emptying delayed
o Slow mouth to anus transit time
why does GOR in a child improve?
LOS develops
what is duodenal atresia?
blockage in the duodenum
how does duodenal atresia present?
vomiting (maybe an hour or 2 after feeding)
how does an x-ray of duodenal atresia present?
classic double bubble
how does a diaphragmatic hernia present?
• Presents w severe respiratory distress bc of pulmonary hypoplasia
where does a diaphragmatic hernia occur?
posterolateral aspect of the diaphragm
what causes alongation and rotation of the midgut?
rapid growth
name midgut developmental abnormalities?
- Jejunal atresia
- Malrotation
- Meckel’s diverticulum
- Omphalocele – gut is outside the baby’s body
- Gastrochisis
how does jejenal atresia present?
presents as vomiting with BILE (not seen in other atresias – bile only present in jejenum)
how can jejunoileal atresia be classified?
• I, II, IIIa, IIIb (apple peel), IV
what happens in malrotation, what does it cause and how is it treated?
- Bowel twisted around the superior mesenteric artery necrotic, gangrenous gut
- Treated by unwinding the bowel and seeing if the blood supply returns
what is the duodenum-jejenum junction anchored by?
ligament of Treitz
what causes intestinal malrotation?
failure of normal rotation and fixation
- Duodenojejunal junction is to the right of the spine
- Ligament of Treitz is absent
- Abnormal placement of mesenteric ligaments may obstruct the second portion of the duodenum
what does persistence of the vitelline duct give rise to?
Meckel’s diverticulum
how does Meckel’s diverticulum occur?
- vitelline duct loses connection to the midgut loop before it goes to the abdominal cavity
- perisstence of proximal part forms MD
- MD attached to terminal ileum
- ectopic gastric mucos or pancreatic tissue may be present in MD
what hindgut abnormalities can occur?
anorectal abnormalities
what gives rise to the rectum and urogenital sinus?
cloaca
what do neural crest cells give rise to?
enteric ganglia
what does Hirschprung’s disease result from?
failure of development of the enteric ganglia (no ganglion cells)
how does Hirschsprung’s disease occur?
failure of neural crest cells to migrate to the correct location leads to absence of ganglion cells
how does Hirschsprung’s disease present?
neonatal colonic obstruction
how does human small intestinal villus and crypt formation occur?
through a process of epithelial and mesenchymal reorganisation
what is the surface area of the small intestine increased by?
- Folding of the mucosa into plicae circulares
- Formation of villi
- Development of microvilli
when is intestinal elongation rapid?
in utero
when do most small intestinal microvillus enzymes begin to appear?
8 weeks
when does • Small intestinal lactase activity reach maximal levels?
end of gestation
when are fetuses unable to swallow/breathe?
before 32-34 weeks of gestation
when do teeth appear?
6 months of age
how is breast’s milk different to cow’s milk?
• Lower protein in breast milk
o More Whey protein > Casein – whey more easily digested
• Lower minerals eg Na – lower solute load on the baby
• Essential fatty acids – better absorbed
• Lipase - digestion
• Anti-infective -
• Vitamin A/C/D greater
• Lower calcium and phosphorus (high phosphorus in CM leads to hypocalcemic tetany)
when can you stop using infant formula?
12 months
when should weaning be introduced?
6 months
when should allergenic food be introduced?
6 months
what foods can be considered allergenic?
eggs
gluten containing food
how should eggs be introduced?
egg yolk first, then egg whites
