1.
A congenital diaphragmatic hernia may result from failure of the
Correct Answer
B. Pleuroperitoneal membranes to fuse in a normal fashion
Explanation
The formation of the diaphragm occurs through the fusion of tissue from four different sources. The pleuroperitoneal membranes normally fuse with the three other components during week 6 of development. Abnormal development or fusion of one or both of the pleuroperitoneal
membranes causes a patent opening between the thorax and abdomen through which abdominal viscera may herniate.
2.
A congenital diaphragmatic hernia most commonly occurs
Correct Answer
D. On the left posterolateral side
Explanation
Congenital diaphragmatic hernias occur most commonly on the left posterolateral side. The pleuroperitoneal membrane on the right side closes before the left for reasons that are not clear. Consequently, the patency on the left side remains unclosed for a longer time. The portion
of the diaphragm formed by the pleuroperitoneal membrane in the newborn is located posterolateral.
3.
A congenital diaphragmatic hernia is usually life-threatening because it is associated with
Correct Answer
A. Pulmonary hypoplasia
Explanation
The herniation of abdominal contents into the pleural cavity compresses the developing lung bud, resulting in pulmonary hypoplasia. Lung development on the ipsilateral (left) side of the herniation is most commonly affected, but lung development on the contralateral (right) side
can also be compromised. The lungs may achieve normal size and function after surgical reduction of the hernia and repair of the diaphragm. However, mortality is high owing to pulmonary hypoplasia.
4.
An 8-day-old boy presents with a history of complete loss of breath at times and of turning blue on a number of occasions. If the baby is placed in an upright or sitting position, his breathing improves. Physical exam reveals an unusually flat stomach when the newborn is lying down; auscultation demonstrates no breath sounds on the left side of the thorax. What is the diagnosis?
Correct Answer
D. Congenital diapHragmatic hernia
Explanation
Loss of breath and cyanosis result from pulmonary hypoplasia associated with congenital diaphragmatic hernia. Placing the baby in an upright position reduces the hernia somewhat and eases the pressure on the lungs, thereby increasing the baby's comfort. The baby's stomach is flat (instead of the plump belly of a normal newborn) because the abdominal viscera have herniated into the thorax. Auscultation reveals no breath sounds on the left side because of pulmonary hypoplasia.
5.
During week 4, the developing diaphragm is located at
Correct Answer
A. C3, C4, C5
Explanation
Although it may seem unusual, the adult diaphragm has its embryologic beginning at the cervical level (C3, C4, C5). Nerve roots from C3, C4, and CS enter the developing diaphragm, bringing both motor and sensory innervation. With the subsequent rapid growth of the neural tube, there is an apparent descent of the diaphragm to its adult levels (thoracic and lumbar). However, the diaphragm retains its innervation from C3, C4, and CS, which explains the unusually long phrenic nerves.
6.
An apparently healthy newborn with a hardy appetite has begun feedings with formula. When she is laid down in the crib after feeding, she experiences projectile vomiting.
Which of the following conditions is a probable cause of this vomiting?
Correct Answer
B. EsopHageal hiatal hernia
Explanation
An esophageal hiatal hernia is a herniation of the stomach through the esophageal hiatus into the pleural cavity. This compromises the esophagogastric sphincter so that stomach contents can easily reflux into the esophagus. The combination of a full stomach after feeding and lying down in the crib will cause vomiting in this newborn.
7.
Pancreatic islets consist of alpha, beta, and delta cells, which secrete glucagon, insulin, and somatostatin, respectively. These cells are derived from
Correct Answer
B. Endoderm
Explanation
Pancreatic islets form as isolated clumps of cells that bud from endodermal tubules.
8.
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?
Correct Answer
D. Extrahepatic biliary atresia
Explanation
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.
9.
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 examination, a small knot is palpated at the right costal margin. Which of the following disorders might be suspected?
Correct Answer
C. HypertropHic pyloric stenosis
Explanation
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.
10.
Which of the following arteries supplies foregut derivatives of the digestive system?
Correct Answer
A. Celiac trunk
Explanation
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.
11.
The most common type of anorectal malformation is
Correct Answer
C. Anorectal agenesis
Explanation
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.
12.
The simple columnar or cuboidal epithelium lining the extrahepatic biliary ducts is derived from
Correct Answer
B. Endoderm
Explanation
The epithelium lining the extrahepatic biliary ducts is derived from endoderm. The intrahepatic biliary ducts are also derived from endoderm.
13.
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 examination 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 examination.
Which of the following conditions would be suspected?
Correct Answer
E. Colonic aganglionosis
Explanation
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.
14.
Which one of the following structures is derived from the midgut?
Correct Answer
A. Appendix
Explanation
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
15.
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 the umbilicus at times. What is the most likely diagnosis?
Correct Answer
D. Ileal diverticulum
Explanation
This baby girl has an ileal diverticulum (Meckel's diverticulum), which occurs when a remnant of the vitelline duct persists. In this case, a fistula is present whereby contents of the ileum can be discharged onto the surface of the skin.
16.
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
Correct Answer
A. OmpHalocele
Explanation
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.
17.
Kupffer cells present in the adult liver are derived from
Correct Answer
A. Mesoderm
Explanation
Kupffer cells are actually macrophages and are derived from mesoderm. Hepatocytes and the epithelial lining of the intrahepatic biliary tree are derived from endoderm.
18.
The simple columnar and stratified columnar epithelia lining the lower part of the anal canal is derived from
Correct Answer
C. Ectoderm
Explanation
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
19.
A baby born to a young woman whose pregnancy was complicated by polyhydramnios was placed in the intensive care unit because of repeated vomiting containing bile. The stomach was markedly distended, & only small amounts of meconium had passed through the anus. What is the most likely diagnosis?
Correct Answer
E. Duodenal atresia
Explanation
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.