Lecture 57: Embryology GI PDF

## Lecture 57: Embryology GI ### Atresia - Blockage of a region of the digestive tube, caused by failure to undergo recanalization. ### Congenital Omphalocele - Results from failure of the small intestines to return to the abdominal cavity following physiological herniation. - ~50% are associat...

## Lecture 57: Embryology GI ### Atresia - Blockage of a region of the digestive tube, caused by failure to undergo recanalization. ### Congenital Omphalocele - Results from failure of the small intestines to return to the abdominal cavity following physiological herniation. - ~50% are associated with genetic abnormalities. ### Gastroschisis - A developmental defect in the anterior abdominal wall (usually on the right side). - Results in abdominal viscera protruding out into the amniotic cavity, directly exposed to amniotic fluid which has a corrosive effect on the exposed area. - Other risks include volvulus (loops twisting around each other). ### Meckel's Diverticulum - Results from incomplete degeneration of the vitelline duct. - Normally doesn't present symptoms, but a patent duct (umbilical/vitelline fistula) will allow fecal discharge out of the umbilicus. - Rule of 2's: (normally 2 inches long ~ 2 feet from ileocecal junction in 2% of the population). ### Accessory Pancreatic Tissue - Can appear anywhere along the developing gut tube, including the vitelline duct (often detected w/ Meckel's diverticulum). - Usually no symptoms under normal conditions. ### Annular Pancreas - A rare occurrence where the ventral pancreatic bud becomes bifid, forming a ring of pancreatic tissue around the descending duodenum. - Normally doesn't present problems, but can become an issue if pancreatic tissue becomes inflamed (eg. pancreatitis), leading to stenosis of the duodenum. ### Min Complications - A (Nonrotation): The cecum & appendix are on the left side - B (Mixed Rotation): The cecum is first to return and becomes fixed to the posterior wall, followed by the return of the ileum. - C (Reverse Rotation): The duodenum lies anterior to the superior mesenteric artery and the transverse colon lies posterior to it, causing stenosis. - D (Subphrenic cecum & appendix): The cecum becomes fixed upon returning from physiological herniation. - E (Internal hernia): The mesentery of the large intestine covers the mesentery of the small intestines upon returning from physiological herniation. - F (Midaut volvulus): The large intestine returns first. The cecum does not become fixed to the posterior abdominal wall and remains suspended by its mesentery, causing duodenal obstruction. **Diagram of the various outcomes of malrotation:** - The diagram shows the different positions of the intestines in the abdominal cavity after malrotation. - It demonstrates that the normal position of the intestines is on the right side, and the reverse position is on the left side. - The diagram shows that if the intestines don't rotate properly, it can lead to a variety of complications, including volvulus (twisting of the intestines) and bowel obstruction.