Question 1

Endodermal contact with the notochord during early GI development is essential for the development of what organ?&#10;A) Liver&#10;B) Pancreas&#10;C) Anorectal sphincter&#10;D) Gallbladder

Accepted Answer

Endodermal contact with the notochord during early GI development is essential for the development of the pancreas.

Question 2

With regard to cytodifferentiation of the GI glandular epithelium along the radial axis,what cell signaling interaction(s)mediate the proliferation,migration,and differentiation of cells within the glandular epithelium?

A) Ephrin ligands and EphB receptors
B) Wnt ligand and Frizzle receptors
C) Tgfß and their receptors (yes)
D) Shh and Ptch1 receptors
E) All the above

E

Accepted Answer

All the choices listed (A, B, C, D) are involved in the processes of proliferation, migration, and differentiation of cells within the glandular epithelium of the gastrointestinal tract. Ephrin ligands and EphB receptors are involved in cell positioning and boundary formation. Wnt signaling, through Wnt ligands and Frizzled receptors, is crucial for the regulation of cell proliferation and differentiation. TGF-β signaling plays a role in cell growth, differentiation, and migration. Shh (Sonic Hedgehog) signaling, through interaction with Ptch1 receptors, is important for the organization and patterning of the gastrointestinal tract.

Question 3

Which of these organs remains retroperitoneal throughout its development?&#10;A) Transverse colon&#10;B) Pancreas&#10;C) Kidney&#10;D) Stomach&#10;E) Sigmoid colon

Accepted Answer

The kidney remains retroperitoneal throughout its development, meaning it is located behind the peritoneal membrane that lines the abdominal cavity. The other organs listed may shift in position during development and may not remain retroperitoneal.

Question 4

What forms the definitive anorectal canal?&#10;A) It is completely derived from the distal hindgut.&#10;B) Two thirds of the anorectal canal is derived from the hindgut, and one third is from the anal pit.&#10;C) It is completely derived from the anal pit.&#10;D) It is entirely derived from the cloacal membrane.&#10;E) It is entirely derived from the urogenital sinus.

Accepted Answer

The anorectal canal is formed from the hindgut and the anal pit, with two thirds of the canal being derived from the hindgut and one third from the anal pit. It is not entirely derived from any single structure, such as the distal hindgut, anal pit, cloacal membrane, or urogenital sinus.

Question 5

What cells serve as the progenitors of hepatocytes?&#10;A) Foregut endodermal cells&#10;B) Mesodermal cells of septum transversum&#10;C) Endothelial precursor cells&#10;D) Cholangiocytes

Accepted Answer

Hepatocytes are derived from the endoderm of the developing foregut, which also gives rise to the pancreatic and biliary cells. Mesodermal cells of septum transversum are involved in the formation of the liver bud, but not in the differentiation of hepatocytes. Endothelial precursor cells do not give rise to hepatocytes. Cholangiocytes are differentiated cells of the biliary tree and are not involved in the development of hepatocytes.

Question 6

Based on hospital records,a 3-day-old newborn has not had a bowel movement.Upon re-examination,you notice the baby's abdomen appears bloated and the infant is beginning to run a fever.Soon after feeding,the baby also exhibits severe vomiting and can't keep anything down.As a physician,you request abdominal x-rays,and you find that the jejunum is drastically dilated,with the remainder of the lower small large intestines appearing smaller in diameter than expected.What is the likely cause?

A) An umbilical hernia
B) Pyloric atresia
C) Meckel's diverticulum
D) Hirschsprung's disease
E) An annular pancreas

Accepted Answer

The symptoms described, including a bloated abdomen, fever, severe vomiting, and the specific findings on the abdominal x-ray (drastically dilated jejunum with the remainder of the lower small and large intestines appearing smaller in diameter), are indicative of Hirschsprung's disease. This condition is characterized by the absence of ganglion cells in the distal colon, leading to a functional obstruction and these clinical manifestations.

Question 7

Based on animal studies,neural crest cells forming the parasympathetic ganglia of the descending colon,sigmoid colon,and rectum originate from which levels of the axis?&#10;A) Only somite 1-7 axial levels&#10;B) The adrenal gland axial levels&#10;C) Only the sacral axial levels&#10;D) Both vagal and sacral levels

Accepted Answer

The parasympathetic ganglia of the descending colon, sigmoid colon, and rectum are formed from neural crest cells originating from both the vagal and sacral levels of the axis, based on animal studies.

Question 8

Clinical testing shows that a newborn has a bowel obstruction caused by a volvulus.Further assessment reveals that the infant's cecum and colon occupy the left abdominal side.Recognizing this is a congenital rotational anomaly,what patterns of gut rotation during GI development could have led to this situation?

A) The initial 90-degree counterclockwise rotation of the intestinal loop occurred, but subsequent rotational steps failed.
B) The initial 90-degree counterclockwise rotation of the intestinal loop occurred, which was followed subsequently by another 180-degree counterclockwise rotation.
C) Each limb of the intestinal loop rotated separately, with only the cranial intestinal limb rotating 90 degrees counterclockwise in the initial rotational step and only the caudal limb rotating 180 degrees counterclockwise during the second rotational step.
D) The initial 90-degree counterclockwise rotation of the intestinal loop occurred, but the subsequent 180-degree rotational step was in the clockwise direction.

Accepted Answer

The initial 90-degree counterclockwise rotation is a normal part of embryonic gut development, but for the cecum and colon to end up on the left side of the abdomen, the subsequent steps of rotation, which normally involve an additional 180-degree counterclockwise rotation, must have failed. This failure results in an abnormal positioning of the intestines, leading to conditions such as volvulus.

Question 9

A 2-year-old male infant is crying because of abdominal pain.Recently,he also began producing bloody stools.Barium enema and x-ray imaging show a bowel obstruction and intestinal ulceration in the ileum about 2 feet proximal to the ileocecal junction.What is the likely diagnosis?

A) Meckel's diverticulum
B) Hirschsprung's disease
C) Omphalocele
D) Umbilical hernia

Accepted Answer

Meckel's diverticulum can lead to bowel obstruction and intestinal ulceration, which matches the symptoms and findings described. It is a congenital condition resulting from the incomplete obliteration of the vitelline duct, with the diverticulum often located about 2 feet from the ileocecal valve.

Question 10

What structure gives rise to the greater omentum?&#10;A) Ventral mesogastrium&#10;B) Dorsal mesogastrium&#10;C) Transverse mesocolon&#10;D) Septum transversum

Accepted Answer

The greater omentum arises from the ventral mesogastrium, which is a double layer of peritoneum that connects the stomach and other abdominal organs to the anterior abdominal wall.

Deck 15: Development of the Gastrointestinal Tract