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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. Which branchial apparatus develops into the thymus?
28 week onward
3rd pouch
2nd; 2nd
Obliterated; forms tunica vaginalis

2. What is the Eisenmeger complex?
Mid gut to yolk sac; omphalomesenteric duct; 7th week
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
When left to right shunting switching to right to left shunting
Amniotic cavity and yolk sac

3. At what week does the fetus look like a baby?
Ventral shaft of penis (penile urethra); labia minora
Week 8
Mesoderm
Bone/cartilage and nerves

4. What is used to keep the PDA open?
Prostaglandins
Neuroectoderm
Cranio - caudal; segmental
Turners; inferior

5. Septum primum (patent foramen oval) caused by excessive resorption of...
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)
elevated AFP
Folate antagonists
septum primum and/or secundum

6. In both meningocele and myelomeningocele the dura...
Where the epiblast and hypoblast fuse
is no longer intact
Week 8
Neural crest cells

7. When does the notochord form? and When does the neural plate form?
Mesoderm
Mesoderm
Mesoderm; 3 week
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast

8. What is DiGeorge syndrome and What does it result in?
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Neural plate; closes by week 4
Obliterated
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects

9. As a horseshoe kidney ascends during kidney development - What do they get trapped under?
Failure of the urachus to obliterate
Spinothalamic first
IMA
Telencephalon

10. What is the difference between agenesis and aplasia?
Decreases
Embryonic period; 1st trimester
Mesoderm
No organ in each; agenesis no primordial tissue

11. Where is sonic hedgehog gene produced? What axis is it responsible in patterning?
Cytotrophoblast
Amniotic cavity and yolk sac
No organ in each; agenesis no primordial tissue
Base of limbs in the zone of polarizing activity; ant - post

12. What artery is derived branchial (aortic) arch 1?
StyloPharyngeus
Maxillary
Neural crest cells
Prevent recurrent UTIs

13. What axis is Wnt 7 responsible for developing?
Mesoderm; nucleous pulposos
Dorsal ventral axis
Neural crest cells
blood entering the RA

14. what drug is used to help close a PDA? what else does this drug treat?
Epispadias
Mid gut to yolk sac; omphalomesenteric duct; 7th week
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Indomethacin; blocks PG production

15. When does hcG get secreted? What does it do?up until when ?
Day 6; maintains corpus luteum; 1st trimester
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
Duodenum to transverse colon; distal transverse colon to rectum

16. Monochorionic - ___________ twins are conjoined
Amniotic epithelium
Pronephros - mesonephros - metanephros; pronephros; most cranially
Maxillary and medial nasal processes
monoamniotic

17. What teratogens can cause discolored teeth?
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3
Surface ectoderm
Tetracyclines
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

18. From What embryonic layer are the schwann cells from ?
Neural crest cells
Prosencephalon - mesencephalon - rhombencephalon
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)
...

19. From what arches are the neural crest cells that form the aorticpulmonary septum derived?
Neuroectoderm
Left horn of the sinus venosus
3 -4 -6
Surface ectoderm

20. Name two endocardial cushion defects.
1st
Endoderm
Ebsteins anomaly; tricuspid atresia
Ventral shaft of penis (penile urethra); labia minora

21. From What embryonic layer do the astrocytes arise?
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility
Surface ectoderm
hypospadias
Neuroectoderm

22. From where does the signal come from to suppress paramesonephric ducts? what stimulates development of the mesonephric ducts?
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
Ventral; failure of urogenital folds to close
Mesoderm
Failure of bony spinal canal to fuse; no; lower vertebral levels

23. What causes persistent Truncus Arteriosus? What does it result in?
IMA
Amniotic cavity and yolk sac
Endometrium
Partial AP septum development; one large vessel leaves the heart - Right to left shunt

24. Which branchial derivative accounts for the sensation and taste in the posterior 2/3 of the tongue? how about the very back?
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
4th arch; 6th arch
Valproate acid
Primitive atrium

25. what results if they dont? What can increase the risks of this?
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
Persistent connection between amniotic cavity and spinal canal; low folic acid
Scrotum; labia majora
Tongue

26. From What embryonic layer do the ANS arise?
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus
Neural crest cells
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric
Cerebellar tonsillar herniation through foramen magnum

27. What is the female remnant of processus vaginalis? male remnant?
Lithium
Obliterated; forms tunica vaginalis
4th pouch
All or none

28. From What embryonic layer does the epidermis arise?
Fluid filled syrinx causes expansion and degeneration of cord tracts
blood entering the RA
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Surface ectoderm

29. What artery is derived branchial (aortic) arch 2?
Telencephalon
Fetal and maternal
Stapedius and hyoid artery
Tetracyclines

30. What is meckel's diverticulum? What is it associated with? What does that cause?
Neural crest cells
Muscles and arteries
Bone/cartilage and nerves
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain

31. From What embryonic layer do the ependymal cells arise?
Neuroectoderm
Neural crest cells
Aortic arch and prox part of subclavian
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3

32. From where to Where is the foregut derivative? midgut? hindgut?
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum
Week 4; week 3
VACTERL; OCPs and maternal diabetes
Aortic arch and prox part of subclavian

33. What hormone is hcG structurally similar too?
LH
Neuroectoderm
2nd pouch
No more umbilical circulation emptying into RA

34. What is an example of a syndrome that can cause abnormal neural crest migration and thus CV abnormalities?
Cytotrophoblast
DiGeorge
Surface ectoderm
3

35. By when are the neuropores supposed to fuse?
Ectoderm
4th week
Neuroectoderm
...

36. What is omphalocele? In What trisomies is it seen?
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Decidual basalis
Endoderm
2nd pouch

37. When is most important to take folic acid to prevent neural tube defects?
Post. sup wall; luteal phase
not covered
Before getting pregnant!
Persistent connection between amniotic cavity and spinal canal; low folic acid

38. Gastroschisis is extrusion of abdominal contents out of abdominal folds ___________ by peritoneum
Lots - cleft palate/lip
1st
not covered
Aminoglycosides

39. What is the notochord? What does the notochord later become?
Mesoderm; nucleous pulposos
Neuroectoderm
Ebsteins anomaly; tricuspid atresia
Initial left to right shunting - then switches

40. From what aortic arch does the stapedial artery arise? the hyoid?
Surface ectoderm
2nd; 2nd
Neural crest cells
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule

41. From What embryonic layer do chromaffin cells arise?
8
Renal artery stenosis;
Synctiotrophoblast
Neural crest cells

42. From where is the pancreas derived? the spleen?
Foregut; dorsal mesentery (mesodermal)
Fallopian tube - uterus - upper 1/3 of vagina
3rd; proximal part of the internal carotid artery
Primitive atrium

43. What does the RET gene encode? what neoplasias is it associated with?
Mesoderm; nucleous pulposos
Dorsal; faulty positioning of genital tubercle
Endoderm
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)

44. For what reason do hypospadias need to be fixed?
Failure of bony spinal canal to fuse; no; lower vertebral levels
Ebsteins anomaly; tricuspid atresia
Prevent recurrent UTIs
Stapedius and hyoid artery

45. ______________ is associated with ventral curvature of the penis
Week 2; bilaminar disk; epiblast and hypoblast
hypospadias
Mesoderm
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen

46. From What embryonic layer do CNS neurons arise?
Urachus/median umbilical ligament; bladder and yolk sac
Mesoderm
From teh lung;blood from IVC in RA to LA; fossa ovalis
Neuroectoderm

47. What germ layer correlates with the branchial pouches?
Ectoderm
Week 8
Week 4; week 3
Endoderm

48. which genital embryology is default? From what duct? what duct degenerates without signal to stay?
Surface ectoderm
Neural crest migration - they then cause spiral
Female; paramesonephric; mesonephric
Week 3; primitive streak formation from the epiblast makes the three layers

49. The spinal cord is made from...
T neuroectoderm
Endoderm
All or none
2; 1

50. What is the neural plate and From what does it form?
Mesoderm
Ectoderm
Grooves/clefts; arches; pouches
Embryonic period; 1st trimester