Embryology — MCQs

A mother brings her 3-day-old son to the pediatrician with a concern over drops of a clear yellow discharge from the clamped umbilical cord. These drops have formed every few hours every day. The vital signs are within normal limits and a cursory physical shows no abnormalities. On closer examination, the discharge is shown to be urine. The skin around the umbilical cord appears healthy and healing. The umbilical cord is appropriately discolored. An ultrasound shows a fistula tract that connects the urinary bladder and umbilicus. Which of the following structures failed to form in this patient?

Research is being conducted on embryoblasts. The exact date of fertilization is unknown. There is the presence of a cytotrophoblast and syncytiotrophoblast, marking the time when implantation into the uterus would normally occur. Within the embryoblast, columnar and cuboidal cells are separated by a membrane. Which of these cell layers begins to line the yolk sac cavity?

A 31-year-old man presents for his annual physical exam. The physician fails to palpate a ductus deferens on the left side. An ultrasound confirms absence of the left ductus deferens and further reveals absence of the left epididymis, seminal vesicle, and kidney. Spermogram and reproductive hormones panel are within normal limits. Left-sided agenesis of an embryonic anlage is suspected. Which two structures are connected by this anlage during embryogenesis?

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?

A 22-year-old G2P1 female presents to the clinic at the beginning of her third trimester for a fetal ultrasound. The sonographer is unable to visualize any of the structures arising from the mesonephric duct in the female fetus. This infant is at risk for malformation of which of the following?

A 2-year-old boy is brought to the emergency department by his mother for evaluation of severe abdominal pain that began one hour ago. On examination, the patient is afebrile and has diffuse rebound tenderness with acute epigastric pain. A stool guaiac test is positive. A small bowel perforation is suspected. What is the embryologic structure that is the underlying cause of this patient’s presentation?

A 52-year-old woman sees you in your office with a complaint of new-onset headaches over the past few weeks. On exam, you find a 2 x 2 cm dark, irregularly shaped, pigmented lesion on her back. She is concerned because her father recently passed away from skin cancer. What tissue type most directly gives rise to the lesion this patient is experiencing?

A 10-year-old boy is brought to his pediatrician over concern for a 2-month history of headaches. Recently, the patient has been experiencing nausea and vomiting, along with some difficulty with coordination during soccer practice last week. On exam, the patient's temperature is 98.2°F (36.8°C), blood pressure is 110/80 mmHg, pulse is 72/min, and respirations are 14/min. On further evaluation, the patient is found to have a well-encapsulated posterior fossa mass. The patient undergoes surgical resection, and the mass is found to be positive for GFAP. Which of the following is derived from the same embryologic germ layer as the cells that comprise this tumor?

A 29-year-old mother brings in her 2-week-old baby boy to a pediatrician because he has been having difficulty feeding. The mother reveals that she had no prenatal care during her pregnancy and gave birth at home without complications. She says that her son seems to be having difficulty sucking, and she occasionally sees breast milk coming out of the infant’s nose. Physical exam reveals that this patient has a gap between his oral and nasal cavities behind the incisive foramen. He is therefore prescribed specialized bottles and his mom is taught positional techniques to ensure better feeding. Failure to fuse which of the following structures is most likely responsible for this patient's disorder?

A six year-old female presents for evaluation of dry skin, fatigue, sensitivity to cold and constipation. The patient’s mother recalls that the patient had surgery to remove a “benign mass” at the base of her tongue 3 months ago because of trouble swallowing. What was the likely cause of the surgically removed mass?