Dev. of GI Flashcards
What does endoderm make up?
- Mucosal epithelium and GI glands
- Except the lower 1/3 of the anus
What does the splanchnic mesoderm make up?
- Connective tissue
- Vasculature
- Smooth muscle wall
What does ectoderm make up?
- Enteric ganglia nerves and glia via neural crest
- Epithelium of lower 1/3 of anus
What are the deravitives of the foregut (6) and what supplies it?
- Esophagus
- Stomach
- Liver
- Gallbaldder
- Pancreas
- Upper duodenum
Celiac trunk
Midgut derivatives (7) and arterial supply?
- Lower duodenum
- Jejunum
- Ileum
- Cecum
- Appendix
- ascending colon
- Proximal 2/3 transverse colon
SMA
Hindgut derivatives (5) and arterial supply?
- Distal 1/3 transverse colon
- descending colon
- sigmoid colon
- rectum
- upper anal canal
IMA
What are the dorsal mesentery derivatives?
-
Greater omentum
- gastrosplenic, gastrocolic, splenorenal ligaments
- Small intestine mesentary
- mesoappendix
- Transverse mesocolon
- Sigmoid mesocolon
Ventral mesentery derivatives?
-
Lesser omentum
- Hepatoduodenal and hepatogastric ligaments
- Falciform ligament of liver
- Coronary ligament of liver
- Triangular ligaments of liver
Lesser = Liver
What organs are retroperitoneal?
Suprarenal glands
Aorta
Duodenum (2nd and 3rd parts)
Pancreas
Ureters
Colon ascending and descending
Kindeys
Esophagus
Rectum
Sad Pucker
Describe how the stomach rotates in development?
The left side rotates ventrally and the right side dorsally
It will drag the dorsal mesentery to become greater omentum and ventral mesentery to lesser omentum
Vagus nerve: LARP - left anterior, right posterior
What is hypertrophic pyloric stenosis?
Faulty migration of neural crest cells, the ganglion cells of enteric nervous system are not properly populated.
- The sphincter cannot properly relax and the pyloric lumen is narrow so food cannot pass
- Presents with a palpable olive mass at right costal margin
- Projectile non bilious vomit after feeding
- Fewer and smaller stools
- failure to gain weight
What interesting job does the liver do in utero at week ten?
Takes over hematopoesis
What do the liver and its derivatives form from?
- Begins as hepatic diverticulum from gut endoderm
- Connection of diverticulum to foregut via common bile duct
- Endoderm makes hepatocytes, bile ducts and hepatic ducts
- Splanchnic mesoderm makes stromal cells Kupffer and stellate cells
What does the gallbladder form from?
- Begins as cystic diverticulum, an outgrowth from cystic endoderm
- Secondary outpouching off of common bile duct
- Cystic duct connects to the bile duct
- Bile formed by hepatic cells in week twelve
Biliary Atresia?
Congenital and adult forms exist. It is the obliteration of the bile duct and inflammation will replace the duct with fibrotic tissue
Presents with immediate onset of progressive jaundice in infants, white clay stool, dark urine (bilirubin)
Poor prognosis 12-19 month life span
Describe pancreas formation
- Development starts as two endodermal buds from the foregut below the cystic diverticulum
- Ventral bud forms uncinate process and grows into ventral mesentary
- Dorsal bud derivatives are pancreas head body and tail and grows into dorsal mesentary
- The buds develop both endo and exocrine functions
In week five the ventral pancreas migrates around posteriorly to fuse with dorsal pancreas
Describe ventral and dorsal pancreatic ducts
Ventral is main pancreatic duct which connects to duodenum
Dorsal is accessory pancreatic duct
Pancreatic anomalies?
- Acessory pancreatic duct (common)
- Pancreas divisum
- Ventral and dorsal parts dont fuse at week 5 mostly asymptomatic, prone to pancreatitis
- Annular pancreas
- poor migration of pancreas, ring around the second part of duodenum
- Presents with duodenal obstrution, Bilious vomitting, and low birth weight
Spleen formation?
Week four - starts as a mesenchymal condensation that forms in the dorsal mesogastrium
week five - it is fully formed
Mesodermal derivative
Describe midgut rotation in weeks 6 10 and 11.
Week 6 - midgut loop protrudes out and makes a 90 degree turn resulting in the proximal portion on the right (convoluted), and the distal portion on the left developing the cecum.
Week 10 - the proximal portion of loop moves back into the abdomen passing uder the distal portion making another 90 degree counterclockwise turn bringing the cecum to URQ and ascending colon anterior to duodenum
Week 11 - the distal portion of the loop returns making another 90 degree CC turn resulting in the cecum descending into the LRQ carrying ascending colon to end on the right side of abdomen
What is an Omphalocele?
- Herniated bowel doesn’t fully retract back to abdomen
- Herniation through umbilicus and covered by parietal peritoneum
What is Gastroschiscis?
- Abnormal lateral body folding and fusion creates weakness in the wall that allows bowel to herniate OR Connect tissue of skin and hypaxial mm of body wall doesnt form normal resulting in wall weakness
- Not covered bt parietal peritoneum
Meckle’s Diverticulum?
- Failure of yolk stalk connection to midgut to regress remaining connected to umbilicus
- Presents asymptomatic - can lead to abdominal swelling intestinal obstruction, bowel sepsis, and GI bleeding
Rule of 2’s:
- 2% of pop
- 2x more likely in males
- 2% have symptoms
- 2 in long
- presents in first 2 years of life
Malrotation/Non-rotation of Midgut loop?
Completes first CCW rotation but not remaining two
Presents:
- left sided colon right sided small intestines
- Formation of fibrous ladd bands volvulus and duodenal obstruction
