10 GI Embryo Flashcards
What surrounds the endoderm of the embryo
Splanchnic mesoderm
The narrowed opening of the yolk sac is
The vitelline duct
What is in the foregut
Esophagus Stomach Liver Gallbladder Pancreas Upper duodenum
What is in the midgut
Lower duodenum Jejunum Ileum Cecum Appendix Ascending colon Proximal 2/3 of transverse colon
What is in the hindgut
Distal 1/3 of transverse colon Descending colon Sigmoid colon Rectum Upper anal canal
What does the endoderm make in the GI
Mucosal epithelium (mucosa) and GI glands except for lower 1/3 of anus
What does the splanchnic mesoderm make in the GI
Muscular wall (muscularis), vascular elements, CT
What does the ectoderm make in the GI
Enteric ganglia, nerves and glia (NCC)
Epithelium of lower 1/3 of anus
What are the adult derivatives of the dorsal mesentery
- greater omentum - gastrosplenic, gastrocolic, and splenorenal ligaments
- small intestine mesentery
- mesoappendix
- transverse mesocolon
- sigmoid mesocolon
What are the adult derivatives of the ventral mesentery
- lesser omentum - hepatoduodenal and hepatogastric ligaments
- falciform ligament of liver(umbilical V)
- coronary ligament of liver
- triangular ligament of liver
What mesentery does the stomach form in
Ventral and it rotates 90 degrees CCW
What mesogastrum forms the greater omentum
Dorsal
Why does the lesser sac end up behind the stomach
Rotation of stomach
Where is the L vagus on the stomach? R?
L - ventral stomach
R - dorsal stomach
The ______ surface of the stomach becomes ventral and the ________ surface becomes dorsal
Left; right
What causes hypertrophic pyloric stenosis
Inability of the sphincter to relax due to faulty migration of the NCC so ganglion cells of the enteric NS are not properly populated
What symptoms are associated with hypertrophic pyloric stenosis
- projectile, non-bilious vomiting after feeding
- fewer and smaller stools
- failure to gain weight
What is associated with hypertrophic pyloric stenosis
Increase incidence in infants treated with erythromycin
What begins as a diverticulum from gut endoderm
Liver
What does the endoderm differentiate into in the liver
Hepatocytes, bile ducts, hepatic ducts
What does the splanchnic mesoderm differentiate into in the liver
Stromal, kupffer, and stellate cells
What do stellate cells do
Support sinusoidal cells of the liver
What functions as the early hematopoiesis organ
Liver
What percentage of BW is the liver at week 10? At birth?
10%; 5%
Where does the pancreas form
Ventral mesentery
What does the dorsal and ventral pancreas form? When does it fuse
D - head, body, tail
V - uncinate process
5th month
What causes the accessory pancreatic duct
Ventral pancreatic duct that doesn’t disappear
What is the prevalence of accessory pancreatic duct
1/3
What is a pancreas divisum
Ventral and dorsal pancreatic duct don’t connect internally
4% incidence
When is bile formed by hepatic cells
Week 12
Bile duct is initially closed but opens via
Recanalization
What happens if the bile duct doesn’t recanalize
Biliary atresia
What are the extrahepatic or intrahepatic ducts replaced by in biliary atresia
Fibrosis
What are the symptoms of biliary atresia
- progressive neonatal jaundice soon after birth
- white clay colored stool
- dark colored urine
- 12-19 month average survival
- can be treated with liver transplant
When does the spleen form
Week 5 but in week 4 there is a mesenchymal consideration in dorsal mesogastrium
What is special about the spleen
It is derived from the mesoderm and not endoderm
What does the midgut do during formation
Physiologically herniates at week 6 and back in at week 10
How des the ascending and tranverse colon end up anterior
90 degree CCW roatation at 50 days and 180 degree CCW rotation at 70 days
What is an omphalocele
Hernitation through umbilicus with peritoneal covering
What increases the risk of omphalocele
Trisomy 12 or 18
What causes omphalocele
- herniated bowel doesn’t fully retract
- lateral body bolding and fusion fails creating a wall weakness
- CT of skin and hypaxial mm of body wall does not form normally
What is gastroschiscis
Herniation through abdominal wall with no parietal peritoneum covering
What is meckel’s diverticulum
Failure of yolk stalk (vitelline duct) connection to the midgut to regress
What are the rules of 2 with meckel’s diverticulum
2% incidence 2x more common in males 2% have medical symptoms Usually 2 feet proximal to terminal ileum Usually 2 inches long Usually 2 years of age
What can meckel’s diverticulum cause
Abdominal swelling, intestinal obstruction, bowel sepsis, GI bleeding
What is non-rotation of the midgut loop
Completes first 90 degree rotation but does not do the 180 degree complete rotation
What is the consequence of non-rotation of the midgut
Ends up with left-sided colon and right-sided small intestine
What is reverse gut rotation
Completes initial 90 CCW but goes 180 CW so the transverse colon ends up posterior to the duodenum
What is volvulus
Rolled up or twisted intestines
What are the symptoms of volvulus
Acute abdominal pain
Vomiting
GI bleeding
What increases the risk of volvulus
Gut rotation anomalies (non-rotation or reverse rotation)
During what month does the lumen of intestines is temporarily obliterated because of endodermal proliferation
5-6th
What is duodenal stenosis
Partial occlusion due to ineffective recanalization (usually involves the horizontal and/or ascending parts)
What is duodenal atresia
Complete occlusion of lumen
What is intestinal stenosis or atresia commonly associated with
Trisomy 21 (Down’s syndrome)
The separation of the cloaca forms what
Urethra and anus
What allows the distal 1/3 of the anus to be ectodermally derived
Anal plug that is later apoptosed, this is the future pectineal line
What is the vascularization of the proximal 2/3 of the anus? Distal 1/3?
IMA; internal iliac A
What is the innervation of the proximal 2/3 of anus? Distal 1/3?
Inferior hypogastric N; pudendal N
What is the failure of the anal plug to degenerate
Imperforated anus
Can be low, intermediate, high, or atresia
What is hirschsprung disease
Absence of ganglionic plexus due to absence of migration of NCC
What are the symptoms of hirshsprung disease
Increase wall thickenss due to hypertrophy in intestine proximal to aganglionic segment
Lack of peristalsis
Abnormal colonic dilation or distension
What is the treatment of hirschsprung disease
Surgical removal of constricted distal segment
