Development of GI System Flashcards
Cranio-caudal folding pulls in ______ to form the foregut, midgut, and hindgut, beginning at _____ days and complete by ____ days
Endoderm; 20; 26
What germ layer forms the mucosal epithelium and GI glands except for the lower 1/3 anus?
Endoderm
What germ layer forms the muscular wall, vascular elements, and CT elements of the GI tract?
Splanchnic mesoderm
What germ layer forms the enteric ganglia and nerves and glia (neural crest)?
Ectoderm
Endoderm forms the mucosal epithelium and GI glands throughout the entire GI tract EXCEPT for the lower 1/3 anus. The epithelium for the lower 1/3 of the anus comes from the _____ germ layer
Ectoderm
the _____ _____ forms at week 4 and connects the gut tube to the dorsal body wall; it runs along the entire GI tract
Dorsal mesentery
What are the adult derivatives of the embryonic dorsal mesentery?
Greater omentum - gastrosplenic, gastrocolic, and splenorenal ligaments
Small intestine mesentery
Mesoappendix
Transverse mesocolon
Sigmoid mesocolon
The ventral mesentery is found between the ventral body wall and foregut, running from ________ to ________
Septum transversum; umbilical vein
What are the adult derivatives of the embryonic ventral mesentery?
Lesser omentum - hepatoduodenal and hepatogastric ligaments
Falciform ligament of liver
Coronary ligament of liver
Triangular ligament of liver
Why are organs like the ascending/descending colon, duodenum, and bulk of pancreas considered SECONDARILY retroperitoneal?
They were initially suspended within mesentery that later fused with the body wall
[primarily retroperitoneal structures were never included in peritoneal cavity, never suspended by mesentery]
Adult derivatives of foregut
Esophagus Stomach Liver Gallbladder Pancreas Upper duodenum
During stomach rotation, the dorsal mesogastrium enlarges, forming the ____ ____
Greater omentum
During stomach rotation:
The ventral border of the stomach moves to the ____
The dorsal border of the stomach moves to the _____
The left stomach surface becomes ____
The right side becomes ____
Overall a total rotation of ___ degrees occurs
Right
Left
Ventral
Dorsal
90
What is hypertrophic pyloric stenosis
Narrowing of the pyloric lumen obstructing food passage; the muscularis externa in the region hypertrophies forming a palpable mass at the right costal margin
Inability of sphincter muscles to relax d/t faulty migration of NCCs so ganglion cells of enteric nervous system are not properly populated
Symptoms of hypertrophic pyloric stenosis
Mother’s treated with what drug are at higher risk?
Symptoms: projectile non-bilious vomiting after feeding, fewer and smaller stools, failure to gain weight
Increased incidence in infants exposed to erythromycin
The embryonic liver begins as ______ from gut ______, which differentiates into heptocytes, bile ducts, and hepatic ducts
______ ______ differentiates into stromal cells, Kupffer, and stellate cells
Diverticulum; endoderm
Splanchnic mesoderm
The pancreas begins to form when an endodermal bud sprouts into the ___ _____.
_____ _____ and ventral pancreatic bud grow into ventral mesentery, whereas dorsal bud grows into dorsal mesentery
Pancreatic buds develop both ____ and ____ portions
Ventral mesentery
Cystic diverticulum
Endocrine; exocrine
What happens during the 5th month of gestation in terms of pancreas development? Which parts of the pancreas are associated with head, body, tail, and uncinate process?
What happens to the ventral pancreatic duct connection?
Ventral pancreas migrates around posteriorly and fuses with dorsal pancreas
The dorsal pancreas = head, body, tail
Ventral pancreas = uncinate process
Ventral pancreatic duct connection to duodenum is lost as it reconnects to dorsal pancreatic duct (may be retained as accessory pancreatic duct - 33% of population)
What congenital anomaly results when a single pancreatic duct is not formed, but rather remains as 2 distinct dorsal and ventral ducts? What condition are these patients more prone to?
Pancreas divisum
Patients prone to pancreatitis
What congenital anomaly results when the pancreas wraps around the duodenum and compresses it, causing duodenal obstruction or stenosis, bilious vomiting, and low birth weight?
Annular pancreas
Formation of bile by hepatic cells begins during week ___ of development. The bile duct lumen is first closed by opens via ________
12; recanalization
What is biliary atresia?
Obliteration of extrahepatic and/or intrahepatic ducts, which are then replaced by fibrotic tissues d/t acute or chronic inflammation
Symptoms, life expectancy, and treatment of biliary atresia
Progressive neonatal jaundice with onset soon after birth, white clay colored stool, dark urine,
12-19 month average survival, only tx is liver transplant
Spleen development begins during week ____ with mesenchymal condensation in the ____ _____, and the spleen actually forms in week ____
4; dorsal mesogastrium; 5
What germ layer is the spleen derived from?
Mesoderm
Midgut derivatives
Lower duodenum Jejunum Ileum Cecum Appendix Ascending colon Proximal 2/3 of transverse colon
During embryonic development, the size of the abdomen is limited. What does this mean for the development of the midgut structures? During what weeks does this occur?
The lengthening midgut must herniate out into the umbilicus at 6 weeks, then brought back in at 10 weeks when the abdomen is large enough to accomodate it
When the midgut is pushed out into the umbilicus, it undergoes rotation.
The first rotation occurs at ___ days and is _____ degrees counterclockwise, which brings the cecum and future ascending colon to the ____ side.
The second rotation occurs at ___ days and is an additional ____ degrees counterclockwise, bringing the cecum to the ____ quadrant and ascending colon ____ to the duodenum
As the midgut returns to the abdominal cavity around ___ days, the cecum descends to the ____ quadrant carrying the ascending colon along with it so that the ascending colon ends up along the ____ side of the abdomen
50; 90; left
70; 90; LUQ; anerior
73; RLQ; right
[total of 270 degrees rotation bc another 90 degree rotation occurs during week 11 as midgut returns to abdomen]
Summary of midgut rotation:
90 degrees CCW at week ____
+90 degrees CCW at week ____ (total 180)
+90 degrees CCW at week ___ (total 270)
6
10
11
Why is midgut rotation significant in terms of viscera location?
Midgut rotation determines which structures are intraperitoneal, retroperitoneal, and secondarily retroperitoneal
Following midgut rotation, most of the pancreas is considered secondarily retroperitoneal. Which part of the pancreas remains intraperitoneal?
The tail
_______ is a gut malformation where there is herniation through the umbilicus including peritoneal covering
Omphalocele
Increased risk of omphalocele occurs with trisomy ___ or ____
What are some other possible etiologies of omphalocele?
12;18
Etiologies:
-herniated bowel does not fully retract
- lateral body wall folding and fusion fails to occur creating wall weakness allowing bowel to later herniate
- CT of skin and hypaxial musculature of body wall does not form normally, creating wall weakness
What gut malformation is characterized by herniation through the abdominal wall WITHOUT peritoneal covering?
Gastroschisis
What gut anomaly is caused by failure of the yolk stalk (vitelline duct) connection to the midgut to regress and can lead to abdominal swelling, intestinal obstruction, bowel sepsis, and GI bleeding?
Meckel’s diverticulum
Rule of 2’s concerning Meckel’s diverticulum
2% incidence
2x more common in males
2% have symptoms
Usually 2 ft proximal to terminal ileum
Usually 2 inches long
Usually presents at 2 years of age
Compare non-rotation of midgut loop to reverse gut rotation
Non-rotation:
Midgut completes first 90 degree CCW rotation but does not do remaining 180 degree CCW rotation. Ends up with L sided colon and R sided small intestines
Reverse gut rotation:
Completes initial 90 degree CCW rotation but then does a 180 degree CW rotation. Transverse colon ends up posterior to duodenum
______ = rolled up, twisted intestines that present as acute abdominal pain, vomiting, and GI bleeding. Increased risk of this with gut rotation anomalies
Volvulus
During the 5-6th month of development, the lumen of intestines is temporarily obliterated because of ______ proliferation.
Later, _____ form as endodermal cells degenerate, reopening the lumen by the end of embryonic period.
Endodermal; vacuoles
What congenital gut anomalies, commonly associated with trisomy 21, may occur if recanalization does not occur following temporary luminal occlusion during month 5-6 of development?
Duodenal stenosis - partial occlusion, usually involving horizontal and/or ascending parts
Duodenal atresia - complete occlusion
Hindgut derivatives
Distal 1/3 of transverse colon Descending colon Sigmoid colon Rectum Superior 2/3 of anal canal
The ____ _____ partitions the cloaca into a dorsal anorectal canal and a ventral urogenital sinus; it develops fork-like extensions (infoldings) of the lateral cloacal walls that grow toward one another, dividing the cloaca into UG sinus and anal canal - which are opened to the exterior when the ____ _____ ruptures.
Urorectal septum
Cloacal membrane
Compare the rectum to the anus in terms of germ layer and vasculature
Rectum = endoderm, inferior mesenteric aa. and vv. of hindgut
Anus = ectoderm, internal iliac aa. and vv.
The anal rectal lumen is temporarily closed by an epithelial anal plug. _____ surrounding the anal canal proliferates forming anal pit with _____ walls.
The anal plug eventually opens via ______ death
Mesenchyme; ectodermal
Apoptotic
How much of the anal canal is endodermal epithelium?
Superior 2/3 is endodermal epithelium
Lower 1/3 is ectodermal
What is the named line dividing the origin of the hindgut and the anal pit?
Pectineal line
An imperforated anus occurs d/t persistent anal membrane. Low, intermediate, or high distinction is relative to what anatomical structures?
Levator ani mm. and pelvic bony landmarks
Defects due to abnormal urorectal septum can be detected based on the presence of ____ in the ____ of the female or the _____ of the male
Meconium; vagina; urine
After stomach rotation, what innervates the ventral surface vs. the dorsal surface?
Ventral surface = left vagus n.
Dorsal surface = right vagus n.
The upper anal canal develops from the _____ while the lower anal canal develops from the _____, which is an invagination of surface ectoderm caused by a proliferation of mesoderm surrounding the anal membrane
Hindgut; proctodeum
Pancreatic islets consist of alpha, beta, and delta cells, which secrete glucagon, insulin, and somatostatin, respectively. These cells are derived from:
A. Mesoderm B. Endoderm C. Ectoderm D. Neuroectoderm E. Neural crest cells
B. Endoderm
A 2-month-old baby with severe jaundice also has dark-colored urine (deep yellow) and white clay colored stool. Which of the following disorders might be suspected?
A. Esophageal stenosis B. Annular pancreas C. Hypertrophic pyloric stenosis D. Extrahepatic biliary atresia E. Duodenal atresia
D. Extrahepatic biliary atresia
A 28 day old baby is brought to the physician because of projectile vomiting after feeding. Until this time, the baby has had no problems in feeding. On exam, a small knot is palpated at the right costal margin. Which of the following disorders might be suspected?
A. Esophageal stenosis B. Annular pancreas C. Hypertrophic pyloric stenosis D. Extrahepatic biliary atresia E. Duodenal atresia
C. Hypertrophic pyloric stenosis
Which of the following arteries supplies foregut derivatives of the digestive system?
A. Celiac trunk B. Superior mesenteric a. C. Inferior mesenteric a. D. Right umbilical a. E. Intercostal a.
A. Celiac trunk
The most common type of anorectal malformation is:
A. Imperforate anus B. Anal agenesis C. Anorectal agenesis D. Rectal atresia E. Colonic aganglionosis
C. Anorectal agenesis
The simple columnar or cuboidal epithelium lining the extrahepatic biliary duct is derived from
A. Mesoderm B. Endoderm C. Ectoderm D. Neuroectoderm E. Neural crest cells
B. Endoderm
A 4 day old baby boy has not defecated since coming home from the hospital even though feeding has been normal without any excessive vomiting. Rectal exam reveals a normal anus, anal canal, and rectum. However, a large fecal mass is found in the colon, and a large release of flatus and feces follows the rectal exam. Which of the following conditions would be suspected?
A. Imperforate anus B. Anal agenesis C. Anorectal agenesis D. Rectal atresia E. Colonic aganglionosis
E. Colonic aganglionosis
Which of the following is derived from the midgut?
A. Appendix B. Stomach C. Liver D. Pancreas E. Sigmoid colon
A. Appendix
A 3 month old baby girl presents with a swollen umbilicus that has failed to heal normally. The umbilicus drains secretions, and there is passage of fecal material through it at times. What is the most likely diagnosis?
A. Omphalocele B. Gastroschisis C. Anal agenesis D. Ileal diverticulum E. Intestinal stenosis
D. Ileal diverticulum
The midgut loop normally herniates through the primitive umbilical ring into the extraembryonic coelom during week 6 of development. Failure of the intestinal loops to return to the abdominal cavity by week 11 results in the formation of
A. Omphalocele B. Gastroschisis C. Anal agenesis D. Ileal diverticulum E. Intestinal stenosis
A. Omphalocele
Kupffer cells present in the adult liver are derived from
A. Mesoderm B. Endoderm C. Ectoderm D. Neuroectoderm E. Neural crest cells
A. Mesoderm
The simple columnar and stratified columnar epithelia lining the lower part of the anal canal is derived from
A. Mesoderm B. Endoderm C. Ectoderm D. Neuroectoderm E. Neural crest cells
C. Ectoderm
A baby born to a young woman whose pregnancy was complicated by polyhydramnios was placed in the ICU because of repeated vomiting containing bile. The stomach was markedly distended, and only small amounts of meconium had passed through the anus. What is the most likely dx?
A. Esophageal stenosis B. Annular pancreas C. Hypertrophic pyloric stenosis D. Extrahepatic biliary atresia E. Duodenal atresia
E. Duodenal atresia
