2: Development Of The GI System Flashcards
What action forms the foregut, midgut, and hindgut?
Craniocaudal folding of the endoderm
Six organs formed by foregut
- Esophagus
- Stomach
- Liver
- Gallbladder
- Pancreas
- Upper duodenum
Seven organs formed by midgut
- Lower duodenum
- Jejunum
- Ileum
- Cecum
- Appendix
- Ascending colon
- Prox 2/3 of transverse colon
Five organs formed by hindgut
- Distal 1/3 of transverse colon
- Descending colon
- Sigmoid colon
- Rectum
- Upper 2/3 anal canal
BS to foregut, midgut, and hindgut
Foregut: celiac trunk
Midgut: superior mesenteric A
Hindgut: inferior mesenteric A
What forms the vitelline duct
Yolk sac opening
What the three germ layers of the GI tract form
Endoderm: mucosal ep, GI glands
Splanchnic mesoderm: CT, vasculature, smooth muscle walls
Ectoderm: enteric ganglia/nerves/glia, epithelium of lower 1/3 of anus
Two main functions of peritoneum
- Produces fluid to lubricate peritoneum and minimize friction
- Produce Abs, mobilize leukocytes, and localize infection
Boundaries of the epiploic foramen
Hepatoduodenal lig, 1st part of duodenum, peritoneum covering IVC and from liver to IVC
Three ligaments that form the greater omentum
- Gastrosplenic
- Gastrocolic
- Splenorenal
Two ligaments that form the lesser omentum
- Hepatoduodenal
2. Hepatogastric
Peritoneal ligaments
regional mesenteries connecting one organ with another or to the abdominal wall (named by organs they connect)
3 Peritoneal ligaments besides the ones that form the omenta
- Gastrophrenic
- Transverse mesocolon
- Phrenocolic
Intraperitoneal organs
Are suspended by mesentery inside the peritoneum
List of organs that are retroperitoneal
- Suprarenal glands
- Aorta and IVC
- Duodenum (2nd and 3rd part)
- Pancreas
- Ureters
- Colon
- Kidneys
- Esophagus
- Rectum
(SAD PUCKER)
Secondarily retroperitoneal
Organs that were initially suspended in mesentery but then fused with body wall
Three organs that are secondarily retroperitoneal
Colon, duodenum, bulk of pancreas
Foregut mesentery vs mid and hindgut
Foregut: dorsal + ventral mesogastrium; mid and hindgut only have 1 mesentery
Hypertrophic pyloric stenosis
Narrow pyloric lumen due to muscle hypertrophy around it
What causes hypertrophic pyloric stenosis?
faulty NCC migration-> ganglion cells of enteric NS not properly populated -> Inability of sphincter to relax
How many infants are born with hypertrophic pyloric stenosis?
1 in 500 infants
Presentation of hypertrophic pyloric stenosis
Presents within a few months of birth with a palpable olive/mass at right costal margin, projectile non-bilious vomiting after feeding, few/small stools, failure to gain weight
Congenital anomalies of the liver
Are very rare
Biliary atresia etiology
Obliteration of bile duct or inflammation replaces duct with fibrotic tissue
Presentation of biliary atresia in infants
Immediate onset of progressive jaundice, white clay colored stools, dark urine, poor prognosis (12-19 month lifespan)
How many pts have accessory pancreatic ducts?
33%
Pancreatic divisum
Ventral and dorsal pancreatic buds fail to fuse
Presentation of pancreatic divisum
Mostly asymptomatic, some pts prone to abdominal pain or pancreatitis
Annular pancreas
Pancreatic ring around 2nd part of duodenum due to poor migration of pancreas
Presentation of annular pancreas
Duodenal obstruction/stenosis -> bilious vomiting, low birth weight
What causes imperforate anus
Persistent anal membrane
What causes low, intermediate, or high distinction in imperforate anus?
Levator ani muscle positioning
Other name for Hirschsprung’s disease
Congenital Aganglionic Megacolon
What causes Hirschsprung’s disease
Absence of ganglionic plexus -> colon fails to relax -> lack of peristalsis; due to failure of NCC migration
Presentation of Hirschsprung’s disease
Intestinal wall hypertrophy proximal to a ganglionic segment, abnormal colonic dilation or distention (megacolon), failure to pass meconium (first BM of a newborn), poor feeding, abdominal distention, vomiting, jaundice
Hirschsprung’s genetic mutation
RET gene
Hirschsprung’s is the colon equivalent to what other disease?
Achalasia
Hirschsprung’s in order children
Constipation, swollen belly, malnutrition
Three types of Hirschsprung’s based on how much colon is affected
- Short segment disease (85% of cases): rectosigmoid region
- Long segment disease: rectosigmoid region -> splenic flexure
- Total colonic aganglionosis: affects entire colon
Dx for Hirschsprung’s
Delayed BM 48ish hrs after birth, rectal biopsy, barium enema
Tx for Hirschsprung’s
Surgical removal of affected colon segment, pull through ganglionic colon segments
