Embryology Practice Questions

Question 1

During the third week of development, the blastocyst undergoes a variety of differentiation processes responsible for the formation of the gastrula and, eventually, the embryo. This differentiation creates cell lineages that eventually become a variety of body systems. What cell lineage, present at this date, is responsible for the formation of the liver?

Accepted Answer

Endoderm

Answer

Neuroectoderm

Answer

Syncytiotrophoblasts

Answer

Ectoderm

Answer

Mesoderm

Question 2

A child is born by routine delivery and quickly develops respiratory distress. He is noted to have epicanthal folds, low-set ears that are pressed against his head, widely set eyes, a broad, flat nose, clubbed feet, and a receding chin. The mother had one prenatal visit, at which time the routine ultrasound revealed an amniotic fluid index of 3 cm. What is the most likely underlying cause of this patient's condition?

Accepted Answer

Bilateral renal agenesis

Answer

Unilateral renal agenesis

Answer

An extra 18th chromosome

Answer

Autosomal recessive polycystic kidney disease (ARPKD)

Answer

A microdeletion in chromosome 22

Question 3

A 60-year-old gentleman passes away after a car accident. On routine autopsy it is incidentally noted that he has both a ventral and dorsal pancreatic duct. This incidental finding observed by the pathologist is generated due to failure of which of the following embryological processes?

Accepted Answer

Fusion

Answer

Apoptosis

Answer

Stem cell differentiation

Answer

Notochord signaling

Answer

Neural crest cell migration

Question 4

A newborn is brought to the pediatric clinic by his mother because she has noticed a swelling in the belly while dressing her baby. On physical examination, the newborn is found to have a non-tender upper abdominal mass. The clinician also noticed absent irises and undescended testes in this baby. A magnetic resonance image (MRI) scan of the abdomen shows a mass of intra-renal origin. Which 1 of the following genetic disorders is most probably the cause of this neonate’s symptoms and signs?

Accepted Answer

Deletion 11-p-13

Answer

WT-1 missense mutation

Answer

Duplication of 11-p-15

Answer

Amplification of MYCN (N-myc) proto-oncogene

Answer

Trisomy 18

Question 5

An investigator is studying the teratogenicity of cigarette smoking during pregnancy. He reviews several databases containing data about birth defects and prenatal drug exposures and finds that infants exposed to cigarette smoke in utero are approximately 2 times as likely to have a particular birth defect than unexposed infants. This defect results from abnormal development during the 6th week of gestation, when the maxillary prominences grow medially and fuse first with the lateral and then the medial nasal prominence. The defect is most likely which of the following?

Accepted Answer

Cleft lip

Answer

Cleft palate

Answer

Macrognathia

Answer

Torus palatinus

Answer

Choanal atresia

Question 6

A male newborn is delivered at term to a 26-year-old woman, gravida 2, para 3. The mother has no medical insurance and did not receive prenatal care. Physical examination shows microcephaly and ocular hypotelorism. There is a single nostril, cleft lip, and a solitary central maxillary incisor. An MRI of the head shows a single large ventricle and fused thalami. This patient's condition is most likely caused by abnormal expression of which of the following protein families?

Accepted Answer

Hedgehog

Answer

Wnt

Answer

Homeobox

Answer

Fibroblast growth factor

Answer

Transforming growth factor

Question 7

A 28-year-old male presents to his primary care physician with complaints of intermittent abdominal pain and alternating bouts of constipation and diarrhea. His medical chart is not significant for any past medical problems or prior surgeries. He is not prescribed any current medications. Which of the following questions would be the most useful next question in eliciting further history from this patient?

Accepted Answer

"Can you tell me more about the symptoms you have been experiencing?"

Answer

"Does the diarrhea typically precede the constipation, or vice-versa?"

Answer

"Is the diarrhea foul-smelling?"

Answer

"Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life"

Answer

"Are the symptoms worse in the morning or at night?"

Question 8

A 23-year-old man comes to the physician for evaluation of decreased hearing, dizziness, and ringing in his right ear for the past 6 months. Physical examination shows multiple soft, yellow plaques and papules on his arms, chest, and back. There is sensorineural hearing loss and weakness of facial muscles bilaterally. His gait is unsteady. An MRI of the brain shows a 3-cm mass near the right internal auditory meatus and a 2-cm mass at the left cerebellopontine angle. The abnormal cells in these masses are most likely derived from which of the following embryological structures?

Accepted Answer

Neural crest

Answer

Surface ectoderm

Answer

Neural tube

Answer

Notochord

Answer

Mesoderm

Question 9

An investigator is studying the effects of an antihypertensive drug during pregnancy. Follow-up studies show that the drug can adversely affect differentiation of the ureteric bud into its direct derivatives in fetuses exposed during the first trimester. Which of the following structures is most likely to develop incorrectly in the affected fetus?

Accepted Answer

Collecting ducts

Answer

Proximal convoluted tubule

Answer

Loop of Henle

Answer

Bladder

Answer

Distal convoluted tubule

Question 10

A 13-year-old girl presents to an orthopedic surgeon for evaluation of a spinal curvature that was discovered during a school screening. She has otherwise been healthy and does not take any medications. On presentation, she is found to have significant asymmetry of her back and is sent for a spine radiograph. The radiograph reveals a unilateral rib attached to the left transverse process of the C7 vertebrae. Abnormal expression of which of the following genes is most likely responsible for this finding?

Accepted Answer

Homeobox

Answer

WNT7

Answer

FGF

Answer

PAX

Answer

Sonic hedgehog

Embryology

Study Resources

Lessons

Questions

Flashcards

Lessons

Gametogenesis

Fertilization and zygote formation

Cleavage and blastocyst formation

Implantation

Bilaminar and trilaminar disc formation

Neurulation and neural tube development

Somite formation and derivatives

Placenta and fetal membranes

Limb development

Urogenital system development

Teratogens and critical periods

Practice Questions

Flashcards

About Embryology for USMLE

Lessons in Embryology

Master Embryology