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USMLE Embryo

Instructions:

Answer 50 questions in 15 minutes.
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Match each statement with the correct term.
Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.

This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.

1. What part of the fetal comp of the placenta secretes hCG? is this part on the inner or outer layer of the chorionic villi? does it make cells?
Synctiotrophoblast; outer; no
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)
septum primum and/or secundum
Endoderm

2. What teratogens can cause flipper limbs (limb defects)? What is this drug used for?
Thalidomide; nausea
Mesoderm; 3 week
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
Prosencephalon - mesencephalon - rhombencephalon

3. By what week is there fetal movement?
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
Endoderm
Week 8
secondary palate

4. What embryological structure gives rise to the trabeculated part of the left and right atrium?
Thickened ectoderm at end of each developing limb
Surface ectoderm
Prevent recurrent UTIs
Primitive atrium

5. what invaginates to form the primitive streak?
After; extrinsic
Week 4; week 3
Epiblast
3

6. What connects the thyroid to the tongue? when happens if it doesnt obliterate?
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Mesoderm
Decreased pulmonary resistance in the pulmonary vasculature
Grooves/clefts; arches; pouches

7. The spinal cord is made from...
IX; X
Maxillary
Hypospadias
T neuroectoderm

8. How does annular pancreas present in children?
Post. sup wall; luteal phase
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
Medial palatine processes
Endocardial cushions

9. What day is the chorion formed?
Female; paramesonephric; mesonephric
3
VACTERL; OCPs and maternal diabetes
Synctiotrophoblast

10. For what reason do hypospadias need to be fixed?
Prevent recurrent UTIs
4th pouch
Surface ectoderm
Diencephalon

11. From What embryonic layer does the retina arise?
Amniotic epithelium
Neuroectoderm
Neural crest cells
Muscular ventricular septum; no

12. What is omphalocele? In What trisomies is it seen?
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Muscles and arteries
Thickened ectoderm at end of each developing limb
DiGeorge

13. what muscles are derived from branchial arch 1?
V3; VII
Week 3; primitive streak formation from the epiblast makes the three layers
Muscles of Mastication: Temporalis - masseter - Lateral and Medila pterygoids - Mylohyoid - anterior belly of the digastric - tensor tympani - tensor veli palatini; ant 2/3 of tongue
Ectoderm; endoderm

14. What is the effect of teratogens after week 8?
Deformation
Folate antagonists
Germinal matrix hemorrhage
Increased AFP and acetycholinesterase (not ACh!) in CSF

15. From what region does the midbrain form from?
Decreased separation of hemispheres across midline; cyclopia
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari
Neural crest cells
Mesencephalon

16. what chemo drugs can cause neural tube defects in the fetus?
Neural crest cells
Folate antagonists
Turners; inferior
...

17. From what region does the cerebral hemisphere form?
Vascular accident intra uterine; apple peel atresia
is no longer intact
Surface ectoderm
Telencephalon

18. What causes meconium discharge from the umbilicus?
Endoderm
not covered
A vitelline fistula - failure of vitelline duct to close
Obliterated; forms tunica vaginalis

19. What is jejunal - ileal - colonic atresia usually due to? What do you see on x ray?
Maxillary
Vascular accident intra uterine; apple peel atresia
All 3
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum

20. Most myelomeningoceles present in the _______ region
Endoderm
Mesoderm
lumbosacral
Week 4; week 3

21. what other facial defect other than cyclopia is associated with holoprosencephaly?
primary palate
Excessive resorption of septum primum or secondum (or both)
Common carotid and internal carotid
Cleft lip/palate

22. What gene is produced in the zone of polarizing activity?
Sonic Hedgehog
28 week onward
Urachus/median umbilical ligament; bladder and yolk sac
Post. sup wall; luteal phase

23. Other than not having a brain - what else is a symptom of anencephaly? why? hint: think about amniotic fluid
Germinal matrix hemorrhage
Surface ectoderm
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Polyhydramnios

24. From where does the permanent kidney for? is it most caudal or most cranial?
pyloric stenosis
OCPS and maternal diabetes
Outgrowth of mesonephric as ureteric bud; most caudal
Neuroectoderm

25. What axis does the basal plate form? what neural system does it become?
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
Neural crest cells
Ventral ; motor
3 -4 -6

26. What embryological structure gives rise to the trabeculated parts of the left and right ventricle?
Week 3; primitive streak formation from the epiblast makes the three layers
Primitive ventricle
Apical ectodermal ridge
Nicotine; preterm labor

27. What hormones are in charge of external genitalia development in the fetus? (in both male and female)
DHT; estrogen
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Week 4
Mesoderm; 3 week

28. What is a syrinx? Where is it found in syringomelia? What is it associated with?
Branchial arch 2
Mesoderm
Mesonephros; male genital system
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II

29. From What embryonic layer does the neurohypophysis arise?
Mesoderm
Week 3; primitive streak formation from the epiblast makes the three layers
Neuroectoderm
Decreases

30. What does DHT turn the labioscrotal swelling into? estrogen?
hypospadias
Epispadias
Neural crest cells
Scrotum; labia majora

31. What are the aspects of fetal alcohol syndrome?
Aminoglycosides
Mental retardation - holoprosencephaly - facial features - fistulas
Prenatal and perinatal
Cerebellar tonsillar herniation through foramen magnum

32. From What embryonic layer are the cardiovascular - lymphatics and blood from?
Cleft lip/palate
Mesoderm
No more umbilical circulation emptying into RA
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum

33. What is the effect of teratogens before week 3?
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
Neural crest cells
All or none
Pulm art (prox) and ductus arteriosus

34. From what aortic arch does the first part of the maxillary artery arise?
1st
Neuroectoderm
ACE inhibitors - HCTZ
Muscles and arteries

35. What germ layer correlates with the branchial pouches?
Synctiotrophoblast; outer; no
3rd pouch
StyloPharyngeus
Endoderm

36. How do you differentiate a thyroglossal duct cyst from a persistent cervical sinus?
Week 8
Transposition of great vessels (failure to spiral)- right to left shunt; tetralogy of Fallout (right to left shunt caused by skewed development of septum); persistent TA (partial septum development - also right to left shunt)
Persistent connection between amniotic cavity and spinal canal; low folic acid
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont

37. When does the neural tube form and From what does it form?
During; instrinsic
Endoderm
Lots - cleft palate/lip
Neural plate; closes by week 4

38. Where is sonic hedgehog gene produced? What axis is it responsible in patterning?
Nutrient and gas for exchange; endometrium
Cranio - caudal; segmental
Physiologic incomplete muscular ventricular septum
Base of limbs in the zone of polarizing activity; ant - post

39. From what are the umbilical arteries and veins derived from?
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)
Neuroectoderm
Neuroectoderm
Allantois

40. What can vit A in excess cause in the fetus?
Amniotic cavity and yolk sac
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
Aminoglycosides
Lots - cleft palate/lip

41. From What embryonic layer does a craniopharygioma arise?
Surface ectoderm
Neural crest cells
Umbilical - midgut herniates through umbilical ring; SMA
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)

42. From What embryonic layer does the lens of the eye arise?
Surface ectoderm
Mesoderm
septum primum and/or secundum
Amniotic cavity and yolk sac

43. Which parts of the pancreas contribute to the head - uncinate process and main pancreatic duct?
Neural crest cells
Dorsal and ventral buds
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II
Tetracyclines

44. What causes a large posterior fossa in a dandy walker malformation? What is found in this fossa?
DHT; estrogen
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Muscles of Mastication: Temporalis - masseter - Lateral and Medila pterygoids - Mylohyoid - anterior belly of the digastric - tensor tympani - tensor veli palatini; ant 2/3 of tongue
Mesoderm

45. What is the primitive streak? From what layer does it form?
Dorsal; sensory
Week 4; week 3
Mesoderm; epiblast
Tetracyclines

46. ______________ is associated with ventral curvature of the penis
When left to right shunting switching to right to left shunting
hypospadias
IMA
Neural crest cells

47. What layer is the epiblast? hypoblast?
Vascular accident intra uterine; apple peel atresia
Bulbos Cordis; right ventricle entirely
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
Ectoderm; endoderm

48. What is an example of a syndrome that can cause abnormal neural crest migration and thus CV abnormalities?
Surface ectoderm
Congenital and chromosomal abnormalities
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
DiGeorge

49. What is hypoplasia? is primordial tissue present?
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
Incomplete; yes
Prostaglandins
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum

50. Cleft palate is a failure of formation of the...
Valproate acid
secondary palate
OCPS and maternal diabetes
Week 8