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USMLE Embryo

Instructions:

Answer 50 questions in 15 minutes.
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Match each statement with the correct term.
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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 embryologic structure provides the aorticpulmonary septum?
Neural crest migration - they then cause spiral
Renal artery stenosis;
Rhombencephalon
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks

2. What are the two components of the placenta? From What do they form? which one secreted hcG?
Decidual basalis
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
...

3. What is the neural plate and From what does it form?
Occiptal
Foregut; dorsal mesentery (mesodermal)
Ectoderm
Prenatal and perinatal

4. From What embryonic layer do chromaffin cells arise?
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric
Tunica vaginalis not fully fused
Neural crest cells
Neuroectoderm

5. From where did a branchial cleft cyst arise if it found?
Found in lateral neck; from no obliteration of 2-4th clefts
Neuroectoderm
No more umbilical circulation emptying into RA
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II

6. From What embryonic layer does the spinal cord arise?
28 week onward
Neuroectoderm
3
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)

7. Most myelomeningoceles present in the _______ region
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
lumbosacral
Thalidomide; nausea
Failure of bony spinal canal to fuse; no; lower vertebral levels

8. What is the notochord? What does the notochord later become?
Mesoderm; nucleous pulposos
Neural crest cells
Decreased separation of hemispheres across midline; cyclopia
Branchial arch 2

9. Which branchial derivative accounts for the sensation and taste in the posterior 2/3 of the tongue? how about the very back?
External auditory meatus
4th arch; 6th arch
Neural crest cells
Surface ectoderm

10. What is holoprosencephaly? what eye disorder does it result in?
They are the edge of neural plate folding; all over the body
Decreased separation of hemispheres across midline; cyclopia
blood entering the RA
Lots - cleft palate/lip

11. Which branchial derivative accounts for the posterior 2/3 of the tongue?
3rd and 4th arches
Surface ectoderm
Cerebral hemisphere - thalami
Failure of bony spinal canal to fuse; no; lower vertebral levels

12. What causes urine discharge from the umbilicus?
Failure of the urachus to obliterate
Found in lateral neck; from no obliteration of 2-4th clefts
Pronephros - mesonephros - metanephros; pronephros; most cranially
is no longer intact

13. From What embryonic layer does the retina arise?
...
Ventral bud
Prostaglandins
Neuroectoderm

14. what drug is used to help close a PDA? what else does this drug treat?
Occiptal
Indomethacin; blocks PG production
Bone/cartilage and nerves
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)

15. From what aortic arch does the stapedial artery arise? the hyoid?
DHT; estrogen
Bulbos Cordis; right ventricle entirely
2nd; 2nd
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)

16. Which CN allows for taste and sensation in the posterior 1/3 of the tongue? how about the very back ?
Ventral bud
2nd; 2nd
IX; X
No more umbilical circulation emptying into RA

17. What effect does warfarin have on the fetus?
Neural crest cells
Before getting pregnant!
Mesoderm
Hemorrhage - bone deformities

18. what muscles are derived from branchial arch 4? CN?
...
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility
T neuroectoderm

19. What is annular pancreas associated with in infants?
80%
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
Maternally derived; meconium
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum

20. Name a syndrome cleft palate is often seen in
DiGeorge
Umbilical - midgut herniates through umbilical ring; SMA
Hypospadias
DHT; estrogen

21. What is the primitive streak? From what layer does it form?
primary palate
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
Mesoderm; epiblast
StyloPharyngeus

22. From What embryonic layer does the lens of the eye arise?
Surface ectoderm
IMA
Folate antagonists
Obliterated

23. What artery is derived branchial (aortic) arch 6?
Nicotine; preterm labor
Persistent connection between amniotic cavity and spinal canal; low folic acid
3rd; proximal part of the internal carotid artery
Pulm art (prox) and ductus arteriosus

24. What teratogen can cause inhibition of intestinal folate absorption and thus neural tube defects?
Day 6; with implantation
secondary palate
Mesoderm
Valproate acid

25. From What embryonic layer does the olfactory epithelium arise?
Mesoderm
Surface ectoderm
Renal artery stenosis;
Maxillary

26. Where is the decidua basalis derived from?
Endometrium
Synctiotrophoblast; outer; no
Surface ectoderm
When left to right shunting switching to right to left shunting

27. Which arches form the posterior 1/3 of the tongue?
Mesoderm
Ebsteins anomaly; tricuspid atresia
Arches 3 and 4
Week 4; week 3

28. What artery is derived branchial (aortic) arch 1?
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
Neuroectoderm
Maxillary
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'

29. what results if they dont? What can increase the risks of this?
6th aortic arch
During; instrinsic
Persistent connection between amniotic cavity and spinal canal; low folic acid
Neural crest cells

30. How do you differentiate a thyroglossal duct cyst from a persistent cervical sinus?
Left horn of the sinus venosus
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
8

31. Where is sonic hedgehog gene produced? What axis is it responsible in patterning?
Base of limbs in the zone of polarizing activity; ant - post
Decidual basalis
Muscular ventricular septum; no
Hepatic circulation; ligamentum venosum

32. Only _______________________________ are associated with neural tube defects
ACE inhibitors - HCTZ
arnold chiari associated with thoraclumbar myelomeningocele
Apical ectodermal ridge
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3

33. What is an arnold chiari II malformation? through what hole does it herniate?
Prevent recurrent UTIs
Neural plate; closes by week 4
Nicotine; preterm labor
Cerebellar tonsillar herniation through foramen magnum

34. From What embryonic layer do the ependymal cells arise?
4th arch; 6th arch
Neuroectoderm
Greater horn of hyoid; CN IX (styloPharyngeus)
Duodenum to transverse colon; distal transverse colon to rectum

35. What does the vitelline duct connect? What is it also known as? when should it obliterate?
Mid gut to yolk sac; omphalomesenteric duct; 7th week
Week 3-8
Endoderm
Failure of bony spinal canal to fuse; no; lower vertebral levels

36. Which branchial arch derivative is obliterated?
5th
septum primum and/or secundum
Mesoderm
Prevent recurrent UTIs

37. At what week does the fetus look like a baby?
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
Decidual basalis
Week 8
Lithium

38. what closes the ductus arteriousus?
Increase in oxygen concentration which decreases prostaglandin concentration
Embryonic period; 1st trimester
3rd and 4th arches
elevated AFP

39. Which branchial apparatus derivative makes the tympanic membrane of the ear?
Cytotrophoblast and synctiotrophoblast
Pataus; fetal alcohol syndrome
Membrane - all 3 from 1st appartus
VSD

40. When does the neural tube form and From what does it form?
Neural plate; closes by week 4
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
Alkylating agents
Mesoderm; epiblast

41. By what week is there fetal movement?
6th aortic arch
Wolffian; mullerian
Week 8
XII

42. What day is the chorion formed?
Neuroectoderm
Obliterated; forms tunica vaginalis
Embryonic period; 1st trimester
3

43. What secretes hCG?
Synctiotrophoblast; outer; no
Base of limbs in the zone of polarizing activity; ant - post
arnold chiari associated with thoraclumbar myelomeningocele
Synctiotrophoblast

44. What separated myometrium of the uterus from the blastocyst?
Increased AFP and acetycholinesterase (not ACh!) in CSF
Base of limbs in the zone of polarizing activity; ant - post
Decidual basalis
Cerebellar tonsillar herniation through foramen magnum

45. Which branchial apparatus develops into the thymus?
3rd pouch
Stapedius and hyoid artery
External auditory meatus
Nicotine; preterm labor

46. From What embryonic layer are the cardiovascular - lymphatics and blood from?
Mesoderm
Mid gut to yolk sac; omphalomesenteric duct; 7th week
Post. sup wall; luteal phase
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)

47. For what reason do hypospadias need to be fixed?
Dorsal ventral axis
Valproate acid
Prevent recurrent UTIs
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

48. Which cranial nerve innervates the motor function of the tongue?
XII
Indomethacin; blocks PG production
Renal artery stenosis;
Ebsteins anomaly; tricuspid atresia

49. From What embryonic layer does the gut tube derivatives arise (lungs liver - pancreas - parathryroid - thyroid follicular cells - thymus)?
Endoderm
28 week onward
Scrotum; labia majora
Wolffian; mullerian

50. What causes meconium discharge from the umbilicus?
A vitelline fistula - failure of vitelline duct to close
Ventral bud
Vascular accident intra uterine; apple peel atresia
Neuroectoderm