USMLE Step 1 - Problem Drill 02: Embryology Question No. 1 of 10 1. A premature infant is born with a patent ductus arteriosis. Which of the following treatments may be used as part of the treatment regimen? Question #01 (A) VEGF (B) Estrogen (C) Progesterone (D) Testosterone (E) Cyclooxygenase inhibitor Think of a therapy that reduces prostaglandin synthesis. Think of a therapy that reduces prostaglandin synthesis. Think of a therapy that reduces prostaglandin synthesis. Think of a therapy that reduces prostaglandin synthesis. E. Correct! A cyclooxygenase inhibitor such as indomethacin is a typical therapy for patent ductus arteriosis. Patent ductus arteriosus is a congenital birth defect that occurs when the ductus arteriosis fails to close shortly after birth. In babies with PDA, the aorta and pulmonary artery remain connected, allowing oxygen-rich blood from the aorta to mix with oxygen-poor blood from the pulmonary artery. This results in strain on the heart, increasing blood pressure in the pulmonary arteries. Symptoms include fast and/or difficult breathing, poor feeding and weight gain, and sweating with exertion. A small PDA may close itself as the child grows; however, a larger PDA requires medical management with indomethacin (this non-selective cyclooxygenase inhibitor constricts muscle in wall of ductus arteriosis to close it) and possible surgical repair. (E)Cyclooxygenase inhibitor
Question No. 2 of 10 2. Infants with DiGeorge syndrome exhibit abnormalities of the thymus and superior parathyroid glands, suggesting that DiGeorge syndrome affects development of which branchial puch(es)? Question #02 (A) 1 st only (B) 2 nd only (C) 2 nd and 3 rd (D) 3 rd only (E) 3 rd and 4 th Branchial pouch 1 develops to form the middle ear cavity, Eustachian tube and mastoid air cells. Branchial pouch 2 develops to form the epithelial lining of the palantine tonsil. Branchial pouch 2 develops to form the epithelial lining of the palantine tonsil. The dorsal wings of branchial pouch 3 develop to form the inferior parathyroid glands. The ventral wings of branchial pouch 3 develop to form the thymus gland. The dorsal wings of branchial pouch 3 develop to form the inferior parathyroid glands. The ventral wings of branchial pouch 3 develop to form the thymus gland. E. Correct! The dorsal wings of branchial pouch 3 develop to form the inferior parathyroid glands. The ventral wings of branchial pouch 3 develop to form the thymus gland. The dorsal wings of branchial pouch 4 develop to form the superior parathyroid glands. The dorsal wings of branchial pouch 3 develop to form the inferior parathyroid glands. The ventral wings of branchial pouch 3 develop to form the thymus gland. The dorsal wings of branchial pouch 4 develop to form the superior parathyroid glands. (E)3 rd and 4 th
Question No. 3 of 10 3. An infant exhibits blood in stool, intussusception, volvulus, and distal small bowel obstruction. Which of the following anomalies is most consistent with these symptoms? Question #03 (A) DiGeorge syndrome (B) Velofacial syndrome (C) Fetal alcohol syndrome (D) Meckel's diverticulum (E) Patent ductus arteriosis Think of a disease associated with the distal small bowel. Think of a disease associated with the distal small bowel. Think of a disease associated with the distal small bowel. D. Correct! An infant with Merckel s diverticulum would exhibit blood in stool, intussusception, volvulus, and distal small bowel obstruction. Think of a disease associated with the distal small bowel. Meckel s diverticulum is a diverticulum of the distal small bowel and is the most common congenital abnormality of the GI tract. It is the remnant of the vitelline duct or yolk sac and may contain pancreatic tissue or acid secreting ectopic gastric mucosal cells. Symptoms and complications include blood in stool, intussusception, volvulus, and distal small bowel obstruction. (D) Meckel's diverticulum
Question No. 4 of 10 4. Oxygenated blood is delivered to the fetus from which one of the following structures in the umbilical cord? Question #04 (A) Left umbilical artery (B) Right umbilical artery (C) Umbilical vein (D) Urachus (E) Wharton s jelly The umbilical arteries return deoxygenated blood back to the mother via the placenta. The umbilical arteries return deoxygenated blood back to the mother via the placenta. C. Correct! The umbilical vein provides oxygenated blood to the fetus from the mother via the placenta. The urachus carries urinary waste from the fetal bladder back to the mother via the placenta. Wharton s jelly serves as a structural substrate for the umbilical cord structures. Umbilical cord circulation consists of: 2 umbilical arteries which return deoxygenated blood back to the mother via the placenta. 1 umbilical vein which provides oxygenated blood to the fetus from the mother via the placenta. (C)Umbilical vein
Question No. 5 of 10 5. In cardiac embryology, the primitive atria give rise to which one of the following structures? Question #05 (A) Ascending aorta. (B) Coronary sinus. (C) Smooth portions of the atria. (D) Trabeculated portions of the atria. (E) All of the above The ascending aorta develops from the truncus arteriosis. The coronary sinus develops from the left horn of the sinus venosus. The smooth portions of the atria develop from the right horn of the sinus venosus. D. Correct! The trabeculated portions of the atria develop from the primitive atria. One of the answers is correct. The embryonic structures truncus arteriosis gives rise to the ascending aorta and pulmonary trunk. Failure of the ductus arteriosis to close leads to patent ductus arteriosis. (D)Trabeculated portions of the atria.
Question No. 6 of 10 6. Which of the following statements regarding the fetal circulatory system follows the normal course of events at the time of birth? Question #06 (A) Pulmonary vascular resistance drops, the foramen ovale closes and the ductus arteriosis closes. (B) Left atrial pressure drops, the foramen ovale closes and the ductus arteriosis closes. (C) Pulmonary vascular resistance drops, the foramen ovale closes, but the ductus arteriosis remains open. (D) Pulmonary vascular resistance drops, the ductus arteriosis closes, but the foramen ovale remains open. (E) Pulmonary vascular resistance rises, the foramen ovale closes and the ductus arteriosis closes. A. Correct! Pulmonary vascular resistance drops, the foramen ovale closes and the ductus venosum closes. Left atrial pressure rises at the time of birth due to a decrease in pulmonary vascular resistance. The ductus arteriosis normally closes. The foramen ovale normally closes. Pulmonary vascular resistance drops at birth with initial respiration. With the onset of respiration at birth, there is a decrease in pulmonary vascular resistance leading to increased left atrial pressure vs. right, which causes closure of the foramen ovale leaving behind the fossa ovalis. Increased oxygen levels in the blood lead to a decrease in prostaglandins which causes closure of the ductus arteriosis. (A)Pulmonary vascular resistance drops, the foramen ovale closes and the ductus arteriosis closes.
Question No. 7 of 10 7. A child is born with a cleft lip. Which of the following structures failed to fuse together during development? Question #07 (A) Medial nasal process and lateral palatine process. (B) Medial nasal process and nasal septum. (C) Maxillary and medial nasal processes. (D) Nasal septum and lateral palatine process. (E) Palatine process and pharynx. Think of the two structures that come together to form the primary palate. Think of the two structures that come together to form the primary palate. C. Correct! Cleft lip is a congenital anomaly that results from the failure of formation of the primary palate fusion of the maxillary and medial nasal processes. Think of the two structures that come together to form the primary palate. Think of the two structures that come together to form the primary palate. Cleft lip is a congenital anomaly that results from the failure of formation of the primary palate fusion of the maxillary and medial nasal processes. (C)Maxillary and medial nasal processes.
Question No. 8 of 10 8. A child is born cyanotic following a normal delivery, and has a bluish tinge to her skin. What three symptoms must be present to diagnose tetralogy of Fallot? Question #08 (A) Pulmonary stenosis (B) Overriding aorta (C) Ventricular septal defect (D) A and B only (E) A, B and C The child will present with pulmonary stenosis, but this is not the only symptom. The child will present with overriding aorta, but this is not the only symptom. The child will present with ventricular septal defect, but this is not the only symptom. The child will present with pulmonary stenosis and overriding aorta, but these are not the only symptoms. E. Correct! Tetralogy of Fallot (often referred to as blue baby syndrome ) is a congenital heart defect that involves three defects: 1) pulmonary stenosis, 2) overriding aorta and 3) ventricular septal defect. Tetralogy of Fallot (often referred to as blue baby syndrome ) is a congenital heart defect that involves three defects: 1) pulmonary stenosis, 2) overriding aorta and 3) ventricular septal defect. A fourth feature that may be present is right ventricular hypertrophy. (E)A, B and C
Question No. 9 of 10 9. Regarding the embryologic development of the gentio-urinary tract, which of the following statements is true? Question #09 (A) Female development is the default development. (B) In the developing male, the Mullerian duct develops and the Wolffian duct (C) In the developing female, the Wolffian duct develops and the Mullerian duct (D) In the developing male, the Mullerian duct is absent. (E) In the developing female, the Mullerian duct is absent. A. Correct! Female development is the default development. In the developing male, the Wolffian duct develops and the Mullerian duct In the developing female, the Mullerian duct develops and the Wolffian duct In the developing male, the Wolffian duct develops and the Mullerian duct In the developing female, the Mullerian duct develops and the Wolffian duct Female development is the default development with disappearance of the mesonephric duct or Wolffian duct and development of the paramesenteric or Mullerian duct, which progresses to form the fallopian tubes, uterus and a portion of the vagina. Male development is dependent on the SRY gene of the Y chromosome which is responsible for testis-determining factor. The developing testes secrete a paramesenteric or Mullerian duct inhibiting factor and androgens which promote development of the mesonephric or Wolffian duct. (A)Female development is the default development.
Question No. 10 of 10 10. All of the following are associated with fetal alcohol syndrome except for. Question #10 (A) Microcephaly (B) Facial abnormalities (C) Polyhydramnios (D) Limb dislocations (E) Postnatal developmental retardation Microcephaly is associated with fetal alcohol syndrome. Facial abnormalities are associated with fetal alcohol syndrome. C. Correct! Polyhydramnios is not associated with fetal alcohol syndrome. Limb dislocations are associated with fetal alcohol syndrome. Postnatal developmental retardation is associated with fetal alcohol syndrome. Fetal alcohol syndrome refers to congenital anomalies which are secondary to a mother consuming significant amounts of alcohol during pregnancy, including microcephaly, facial abnormalities, heart and lung fistulas, limb dislocations, and pre- and postnatal developmental retardation. Fetal alcohol syndrome is the most common cause of congenital anomalies in the United States. (C)Polyhydramnios