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Exam 5: Embryology

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Question 21

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A 22-year-old man comes to the office due to occasional dull headaches that awaken him from sleep.  The patient has no associated neurologic deficits.  There is no history of migraines in the family.  His temperature is 37.2 C (99 F) , blood pressure is 140/80 mm Hg, pulse is 60/min, and respirations are 12/min.  On physical examination, there are several 3- to 5-cm flat, pigmented spots on his trunk.  There are also multiple, subcentimeter, soft, fleshy, cutaneous tumors located on his trunk and neck.  The predominant cells forming these skin tumors most likely originated from which of the following structures?

A) Endoderm
B) Mesoderm
C) Neural crest
D) Neural tube
E) Notochord
F) Surface ectoderm

G) D) and E)
H) A) and B)

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Question 22

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A 6-hour-old boy is in the newborn nursery with feeding difficulties.  The patient was born at 39 weeks gestation to a 33-year-old primigravida via cesarean delivery due to failure to progress and late decelerations seen on fetal heart tracing.  Apgar scores were 8 and 9, but examination shows an infant with excessive drooling and coughing.  Cardiac, respiratory, and abdominal examinations are otherwise normal at rest.  When the infant attempts to breastfeed, however, several bouts of coughing and perioral cyanosis develop with oxygen saturation of 85% on room air.  Which of the following is the most likely cause of this patient's condition?

A) Atresia of small intestine
B) Collapse of supraglottic structures during respiration
C) Failure of primitive foregut to separate from airway
D) Obstruction of posterior nasal passages
E) Thoracic herniation of abdominal viscera

F) B) and D)
G) A) and E)

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Question 23

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Researchers studying neural crest cell migration in a human fetus observe normal activity beginning at the 8th week of embryogenesis with interruption during the 12th week, when migration is typically completed.  Which of the following structures is most likely to lack innervation as a result of this disruption?

A 30-year-old man comes to the emergency department due to severe abdominal pain.  The patient first developed the pain yesterday, and it has become increasingly worse.  Over the last few hours, he has also developed bilious emesis.  The patient has had no previous surgeries.  Temperature is 37.8 C (100 F) and pulse is 110/min.  Physical examination shows diffuse abdominal tenderness with guarding during palpation.  Abdominal imaging reveals bowel wall thickening within a blind pouch connected to the ileum.  A laparotomy is performed.  During the procedure, a fibrous band is seen attaching the end of the pouch to the umbilicus.  The walls of this pouch are most likely composed of which of the following?

A 38-year-old woman is brought to the emergency department after a motor vehicle collision.  She sustained no injuries in the collision but is adamant that she did not see the car that hit her along the front side of her vehicle.  The patient also reports that she has been having daily headaches and has not menstruated in 4 months.  On physical examination, there is bitemporal hemianopsia but no other abnormalities.  MRI of the brain is shown below. This patient's lesion most likely originates from which of the following embryologic layers?

A newborn girl is evaluated in the neonatal intensive care unit for difficulty breathing.  The patient was born at term via spontaneous vaginal delivery.  Since birth, she has had difficulty breathing with loud snoring sounds and intermittent oxygen desaturations.  She has been unable to breastfeed due to her breathing problems.  Breathing improves significantly when the patient is placed in a prone position.  On examination, there is a small mandible, posteriorly displaced tongue, and U-shaped cleft palate.  The abnormalities described represent an example of which of the following?

A term newborn boy is evaluated in the neonatal intensive care unit for respiratory distress.  Apgar scores are 2 and 5 at 1 and 5 minutes, respectively.  Respirations are 84/min.  On examination, the patient has a barrel chest with a scaphoid abdomen and mild cyanosis of his extremities.  Auscultation shows absent breath sounds on the left; right lung aeration is normal.  Chest x-ray reveals multiple fluid-containing cystic areas on the left and a mediastinal shift to the right.  Which of the following embryologic events most likely failed to occur in this patient?

A 45-year-old woman is brought to the emergency department after a generalized tonic-clonic seizure.  She reports no prior history of seizures, but she has noticed right arm weakness over the last week.  Her family history is significant for her mother's death from skin cancer.  Physical examination shows a skin lesion measuring 13 mm on her back, as shown in the image below. This lesion most likely originated from which of the following embryologic derivatives?

A 7-year-old boy is brought to the office for evaluation of a neck mass.  A week ago, the patient was taken to an urgent care clinic for nasal congestion and sore throat.  The symptoms resolved after a few days, but his parents noticed a persistent neck swelling.  The patient has no prior medical conditions, and his immunizations are up to date.  On physical examination, he appears well and is well nourished.  Neck examination shows a mildly tender, 2-cm, midline mass that moves up when the patient swallows.  Which of the following is the most likely cause of this patient's lesion?

A 4-hour-old girl with a cleft lip is breastfeeding without difficulty.  The infant was born vaginally after an uncomplicated pregnancy and delivery.  Routine antenatal sonography at 20 weeks gestation showed no abnormalities.  Physical examination shows an intact palate and a unilateral cleft lip on the left side.  No other abnormalities are seen.  This child's cleft lip resulted from failure of which of the following intrauterine processes?

A 2-day-old infant is dusky and irritable.  He was born to a 22-year-old primigravida with sporadic prenatal care.  Delivery was uncomplicated, and Apgar scores were 7 and 8 at 1 and 5 minutes, respectively.  His temperature is 36.7 C (98 F) , blood pressure is 70/30 mm Hg, pulse is 148/min, and respiratory rate is 68/min.  Physical examination shows a cyanotic and irritable newborn with mild-to-moderate respiratory distress.  Auscultation reveals a continuous, machine-like murmur appreciated between the scapulae.  Serum lactate is elevated.  Echocardiogram shows the aorta lying anterior, inferior, and to the right of the pulmonary artery.  Failure of which of the following embryologic processes is most likely responsible for this patient's condition?

A 32-year-old man presents to the emergency department with a one-day history of severe abdominal pain along with nausea and vomiting.  His pain is constant and radiates to his back.  He admits to "drinking a few beers" with some friends a couple days ago.  Laboratory studies reveal significantly elevated amylase and lipase.  An abdominal CT shows pancreas divisum, a common congenital anomaly that results from failure of the pancreatic ductal systems of the ventral and dorsal pancreatic primordia to fuse during embryogenesis.  Which of the following pancreatic structures is derived from the ventral pancreatic primordium?

A 3-day-old girl is brought to the emergency department by her parents due to persistent vomiting and refusal to feed.  The vomiting began early in the morning and has been a greenish-yellow color.  The emesis does not contain blood.  The infant appears dehydrated.  Her heart rate is 175/min and blood pressure is within normal limits.  After initial evaluation is complete, the infant undergoes laparotomy.  Findings include a normal-appearing duodenum, the absence of a large segment of jejunum and ileum, and the remainder of the distal ileum winding around a thin vascular stalk.  Which of the following intrauterine processes is most likely responsible for this patient's condition?

A 4-year-old girl is brought to the office after her parents noticed dark red blood on her toilet tissue after a bowel movement.  She has had no abdominal pain, dysuria, or discomfort with defecation.  The girl has no known medical conditions and takes no medications.  Temperature is 36.7 C (98.1 F) , blood pressure is 100/40 mm Hg, and pulse is 112/min.  Examination shows a soft and nontender abdomen, and bowel sounds are present.  Hemoglobin is 8 g/dL, and platelet count is 215,000/mm³.  Coagulation studies are normal.  Sequential imaging using ^99mTc-pertechnetate scintigraphy demonstrates focal radiotracer accumulation in the right lower quadrant.  Which of the following embryologic processes most likely resulted in this patient's condition?

A neonate at 38 weeks gestation is delivered vaginally following an uncomplicated pregnancy.  Immediately after delivery, the neonate has respiratory distress.  Examination shows cyanosis, tachypnea, and poor perfusion.  The patient is emergently intubated, and mechanical ventilation is initiated.  A nasogastric tube is also inserted.  On auscultation, asymmetric aeration with decreased left-sided breath sounds are noted.  The abdomen is scaphoid.  A chest x-ray is shown in the exhibit.  Which of the following is the most likely cause of this patient's respiratory distress?

A 37-year-old woman is brought to the emergency department after developing sudden-onset right arm weakness and difficulty speaking.  She has no significant medical history but takes oral contraceptives.  Examination shows decreased right upper extremity strength and expressive aphasia.  Cardiac auscultation is normal.  MRI of the brain reveals acute infarction in the left frontal lobe.  Further evaluation to determine an etiology is performed.  During echocardiogram, agitated normal saline is injected into a peripheral vein and bubbles are seen passing into the left side of the heart.  Which of the following is the most likely cause of the observed finding in this patient?

Five measurements of blood oxygen saturation taken in a fetus are: 67, 61, 56, 52 and 31%.  The highest value is most likely recorded in which of the following vessels?

A 32-year-old woman, gravida 1 para 0, at 35 weeks gestation comes to the emergency department due to absent fetal movement for the past 24 hours.  The patient has had no prenatal care.  Fetal ultrasonography confirms an intrauterine fetal demise.  Autopsy examination of the fetus reveals incomplete separation of the cerebral hemispheres with a single ventricle, as shown in the image below: Which of the following is most closely associated with this fetal condition?

A 32-year-old woman, gravida 2 para 1, with an uncomplicated prenatal course delivered a 4.1-kg (9-lb) newborn at 39 weeks gestation via spontaneous vaginal delivery.  Apgar scores were 8 and 10 at 1 and 5 minutes, respectively.  Further evaluation in the newborn nursery shows abnormal sexual differentiation.  Karyotype analysis shows a 46,XY genotype.  Biopsy of gonadal tissue shows a lack of Sertoli cells but normally functioning Leydig cells.  Which of the following phenotypes is most likely to be present?

A newborn boy is being evaluated in the nursery.  The patient was born at 39 weeks gestation via cesarean delivery to a 30-year-old primigravida.  Head circumference, weight, and length are at the 75th to 90th percentiles.  The anterior fontanelle is open and soft.  The neck is supple.  Cardiopulmonary examination is unremarkable, and the abdomen is soft.  The back appears unremarkable.  Hip examination shows no hip clicks.  Both feet are plantar flexed and adducted with the soles pointing medially.  There is resistance to range of motion assessment in both feet.  Muscle tone is normal and newborn reflexes are intact.  The abnormal findings on this patient's physical examination most likely represent which of the following types of congenital anomalies?