Embryology.txt

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celloboy7
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192481
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Embryology.txt
Updated:
2013-01-13 00:43:08
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Pathology
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Pathology 1
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  1. A newborn male infant is examined. There is a palpable right testis, but no left testis, in the scrotal sac. The infant has no other abnormalities noted. Which of the following is the most likely abnormality involving the gonads of this infant?
    Incomplete descent
  2. Following ovulation and fertilization of an ovum, a blastocyst develops. Growth and differentiation occurs following implantation. Which of the following will develop into the placenta?
    Trophoblast
  3. A 5-year-old child fatigues easily. On examination a machinery-like murmur is auscultated over his chest. Echocardiography shows shunting of blood from the aorta to the pulmonary artery. An abnormality involving which of the following structures is most likely present in this boy?
    Ductus arteriosus
  4. A 3500 gm infant born at term is doing well and gaining weight normally until the fourth week of life. He then exhibits feeding difficulty with forceful vomiting. Now, on physical examination, no external anomalies are noted. However, there is a firm mass palpable in the upper mid abdominal region. Which of the following conditions is the infant most likely to have?
    Pyloric stenosis
  5. An infant born at term is examined, and there is abnormal fusion of the 3rd, 4th, and 5th digits of the left hand. A radiograph of the left hand shows transformation of metacarpals I, II, III, and V to short, carpal-like bones. A mutation involving which of the following genes most likely led to these findings?
    HOXD13
  6. An infant born at term has a radiograph taken. No congenital abnormalities are noted. The upper heart borders are not visualized. Which of the following structures is most likely to obscure the heart borders in this infant's radiograph?
    Thymus
  7. A secondary oocyte is developing normally. At which of the following times does the second maturation division of meiosis become completed?
    At fertilization
  8. During the 3rd week of embryonic development, splanchnic mesoderm differentiates into blood islands with angioblasts. In what developing tissue site does this process occur?
    Heart
  9. An ovum is fertilized. After 3 weeks a blastocyst implanted on the endometrium has an inner embryoblast and an outer trophoblast. Which of the following is the next step in forming a 3-layered embryonic disk?
    Gastrulation
  10. A 55-year-old man has noted sharp pain in his right lower extremity for the past 2 months. MR imaging of his spine shows impingement on a spinal nerve root by a herniated structure located between L5 and S1. From which of the following embryonic derivatives does this herniated structure most likely arise?
    Notochord
  11. In the developing embryo, pharyngeal arches are formed. The second (branchial) arch gives rise to the stapedius, orbicularis oris, and posterior belly of the digastric muscles. Which of the following cranial nerves is also derived from this arch?
    VII
  12. An infant born at 30 weeks gestation develops respiratory distress soon after birth. the infant is intubated and upon mechanical ventilation there are breath sounds auscultated over the right chest, but not over the left. An abnormality involving a derivative from which of the following embryonic structures is most likely present in this infant?
    Foregut
  13. In the normally developing embryo, aortic arches are apparent by the end of the fourth week. Which of the following arteries is derived from the third pair of aortic arches?
    Carotid
  14. A 19-year-old primigravida gives birth at term following an uncomplicated pregnancy to a 3000 gm male infant. He has not passed any stool by day 2 of life. On physical examination his abdomen is distended. An ultrasound scan shows a dilated colon. Laboratory studies show a normal sweat chloride test. A mutation involving which of the following genes is most likely to be present in this infant?
    RET
  15. A fetus at 18 weeks gestation is normally formed and appropriately sized. No fetal or placental anomalies are present. Which of the following parts of the fetal vasculature is most likely to have the greatest oxygen concentration?
    Umbilical vein
  16. An embryonic eye is developing normally. A retina is present on the posterior aspect of the globe. What is the embryologic origin of the portion of retina containing nerve cell bodies?
    Diencephalon
  17. A newborn examination is performed. The tympanic membranes are visualized bilaterally. What is the embryologic origin of the structure that forms the canal connecting the external ear to the tympanic membrane?
    First pharyngeal cleft
  18. A 2-year-old child has difficulty eating and drinking. On examination, there is a lateral cleft that involves the right upper lip. This defect is most likely due to failure in development and fusion of which of the following?
    Medial nasal prominences and maxillary prominences
  19. A 20-year-old woman is unable to conceive and undergoes an infertility workup. A pelvic ultrasound reveals a bicornuate uterus. Which of the following is the most likely explanation for her anomalous uterus?
    Failure of the paramesonephric ducts to fuse
  20. A newborn boy is noted to be dribbling urine. On examination he has a urethral opening on the ventral-midpoint of his penis. Abnormal development of which of the following structures is most likely responsible for his urinary problem?
    Urethral fold
  21. In a developing embryo, neural crest cells form adjacent to the neural tube. These neural crest cells then undergo migration. Which of the following structures is derived from these migrating cells?
    Dorsal root ganglion
  22. A newborn infant boy is noted to have an abnormality involving his perineum and scrotum. There is failure of midline fusion in the urogenital region. Chromosome analysis shows his karyotype is 46, XY. Which of the following is most likely responsible for his condition?
    Abnormal androgen levels in utero
  23. A neonate undergoes a check of health status. On examination a faint cardiac murmur is auscultated. Echocardiography is performed and shunting of blood is noted from the left atrium to the right atrium. An abnormality in embryonic development of which of the following structures has most likely occurred in this neonate?
    Endocardial cushion
  24. The two superior and two inferior parathyroid glands are found adjacent to the posterior aspect of the thyroid gland. From which of the following are these parathyroid glands derived in embryologic development?
    Pharyngeal pouches
  25. A 29-year-old woman describes mild discomfort with sexual intercourse for the past month. A pelvic examination reveals no vaginal discharge, and the cervix appears normal. On examination she has a small, slightly tender 2 cm mass in the lateral wall of her vagina. The excised mass is cystic, fluid filled, and lined by a cuboidal epithelium. This mass is most likely to be a remnant of which embryologic structure?
    Mesonephric duct
  26. An infant is noted to have respiratory distress soon after birth. Physical examination reveals no external anomalies. A chest radiograph shows a left lung mass. A CT scan shows a peripheral, posterior left lower lobe lung posteriorly, with both cystic and solid components. Thoracic surgery is performed and the left lower lobe is removed without difficulty. There are no adhesions or abnormal vascular connections. Which of the following conditions is most likely to produce these findings?
    Congenital pulmonary airway malformation
  27. A 31-year-old woman has noted no fetal movement by 16 weeks gestation. A fetal ultrasound shows the fetal head contains a brain with thin cortex, single enlarged ventricle, and fused thalami. Which of the following developing regions of the brain is most likely abnormal in this fetus?
    Prosencephalon
  28. During normal embryonic development, anterior-posterior differentiation occurs. By the end of the fifth week, dorsomedial somitic cells give rise to myotomes forming the epimere. Which of the following muscles is most likely derived from these cells?
    Erector spinae

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