Digestive System Embryology Questions

Pancreatic islets form as isolated clumps of cells that bud from endodermal tubules.

The most common type of malformation involving the anal canal and rectum is anorectal
agenesis, in which the rectum ends as a blind sac above the puborectalis muscle. The anal canal
may form normally but does not connect with the rectum. This malformation is accompanied
by various fistulas.

An omphalocele results when intestinal loops fail to return to the abdominal cavity. Instead,
the intestinal loops remain in the umbilical cord covered by amnion.

This baby boy suffers from colonic aganglionosis, or Hirschsprung disease, which results
in the retention of fecal material, causing the normal colon to enlarge. The retention of fecal
material results from a lack of peristalsis in the narrow segment of colon distal to the enlarged
colon. A biopsy of the narrow segment of colon would reveal the absence of parasympathetic
ganglion cells in the myenteric plexus caused by failure of neural crest migration

The epithelium lining the extrahepatic biliary ducts is derived from endoderm. The intrahepatic biliary ducts are also derived from endoderm.

This baby is suffering from duodenal atresia at a level distal to the opening of the common
bile duct. This causes a reflux of bile and its presence in the vomitus. The pregnancy was complicated by polyhydramnios because the duodenal atresia prevented passage of amniotic fluid
into the intestines for absorption.

The appendix is derived from the midgut. The midgut normally undergoes a 270° counterclockwise rotation during development; malrotation of the midgut may result in the appendix
lying in the upper part of the abdominal cavity, which may affect a diagnosis of appendicitis.

This baby girl has an ileal diverticulum (Meckel diverticulum), which occurs when a remnant of the vitelline duct persists. In this case, a fistula is present by which contents of the ileum
can be discharged onto the surface of the skin.

The anal canal is formed from two components—the hindgut and proctodeum. The epithelium lining the lower anal canal is derived from ectoderm lining the proctodeum.

The baby is suffering from extrahepatic biliary atresia, which results from failure of the bile
ducts to recanalize during development. This prevents bile from entering the duodenum

The baby is suffering from hypertrophic pyloric stenosis. This occurs when the smooth
muscle in the pyloric region of the stomach hypertrophies and obstructs passage of food.
The hypertrophied muscle can be palpated at the right costal margin. The exact cause of this
condition is not known.

The artery that supplies foregut derivatives of the digestive system is the celiac trunk. The
celiac trunk consists of the left gastric artery, splenic artery, and common hepatic artery.
The superior mesenteric artery supplies the midgut, and the inferior mesenteric artery supplies
the hindgut.

Kupffer cells are actually macrophages and are derived from mesoderm. Hepatocytes and
the epithelial lining of the intrahepatic biliary tree are derived from endoderm.