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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 inferior parathyroids?
Polyhydramnios
3rd pouch
Excessive resorption of septum primum or secondum (or both)
Day 6; maintains corpus luteum; 1st trimester

2. What produces testis determining factor? what cells are produced from this? and What do they secrete? does this result in?
Congenital and chromosomal abnormalities
Increased AFP and acetycholinesterase (not ACh!) in CSF
Neuroectoderm
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)

3. How does annular pancreas present in children?
...
Ventral bud
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
Increase in oxygen concentration which decreases prostaglandin concentration

4. What are the neural crest cells and where do they come form? where do they go?
Failure of bony spinal canal to fuse; no; lower vertebral levels
Left horn of the sinus venosus
Nicotine; preterm labor
They are the edge of neural plate folding; all over the body

5. From what region of the brain does the aqueduct form?
Stapedius and hyoid artery
Week 3-8
Nutrient and gas exchange
Rhombencephalon

6. From What embryonic layer does connective tissue and muscle arise?
Week 4; week 3
Mesoderm
During; instrinsic
Week 2; bilaminar disk; epiblast and hypoblast

7. What is the prochordal plate?
Where the epiblast and hypoblast fuse
2nd pouch
Dorsal and ventral buds
Endoderm

8. Does malformation occur during or after the embryonic period? is it due to an extrinsic or intrinsic disruption?
Tunica vaginalis not fully fused
During; instrinsic
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
Week 8

9. From What embryonic layer does the brain arise?
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule
Umbilical - midgut herniates through umbilical ring; SMA
Neuroectoderm
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)

10. From where does the pulmonary arteries and the ductus arteriosus arise?
Thalidomide; nausea
Hypospadias
6th aortic arch
Cleft lip/palate

11. Which part of pancreas contribute to body? tail? isthmus? accessory pancreatic duct?
Pataus; fetal alcohol syndrome
4th week
Ventral bud
Endoderm

12. what happens in hydrocele?
Hepatic circulation; ligamentum venosum
Thalidomide; nausea
Mesoderm
Tunica vaginalis not fully fused

13. Which arches form the posterior 1/3 of the tongue?
Allantois
Decreases
Mesdoerm
Arches 3 and 4

14. How is amniontic fluid excreted? How is amniotic fluid resorped?
Primitive ventricle
Arnold chiari; syringomyelia
Mesoderm
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood

15. is epispadias or hypospadias associated with exstrophy of the bladder?
Truncus arteriosus; pulmonary trunk
Endoderm
Folate antagonists
Epispadias

16. How many umbilical arteries are there? How many umbilical veins?
Cytotrophoblast
DiGeorge
2; 1
4th week

17. What is the leading cause of birth defects in the US? what else is this perpetrator the leading cause of?
Mesoderm
Increased AFP and acetycholinesterase (not ACh!) in CSF
Fetal alcohol syndrome; mental retardation
Outgrowth of mesonephric as ureteric bud; most caudal

18. From What embryonic layer are the cardiovascular - lymphatics and blood from?
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Mesoderm
septum primum and/or secundum
Right common cardinal vein and right anterior cardinal vein

19. What is the fate of the cervical sinuses that develop from the 2nd -4th branchial grooves?
Valproate acid
Apical ectodermal ridge
Surface ectoderm
Obliterated

20. What part of the gut rotates around the SMA? and At what point?
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
Midgut; 10th week
Mesoderm
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects

21. From What embryonic layer is the kidney and the adrenal cortex from?
Mesoderm
3rd pouch
Endometrium
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)

22. What is DiGeorge syndrome and What does it result in?
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
arnold chiari associated with thoraclumbar myelomeningocele
septum primum and/or secundum
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects

23. WithIn what week does gastrulation occur? What is gastrulation?
Week 3; primitive streak formation from the epiblast makes the three layers
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
Neuroectoderm
1st

24. From where does the signal come from to suppress paramesonephric ducts? what stimulates development of the mesonephric ducts?
Oxygenated; placenta to fetus (IVC)
Epiblast
elevated AFP
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells

25. what bone/cartilage and nerves are derived from branchial arch 3?
Mesoderm
Greater horn of hyoid; CN IX (styloPharyngeus)
Allantois
Diencephalon

26. Which branchial apparatus develops into the superior parathyroids?
Telencephalon
Ventral bud
4th pouch
Mesdoerm

27. Cleft lip is a failure of formation of the...
primary palate
Endoderm
Yolk sac; 3rd week
Membrane - all 3 from 1st appartus

28. What day is the amnion formed?
Mesoderm
Neural crest migration - they then cause spiral
8
Branchial arch 2

29. From what aortic arch does the common carotid artery arise? what else arises from this arch?
Urachus/median umbilical ligament; bladder and yolk sac
Mesoderm
3rd; proximal part of the internal carotid artery
Allantois

30. What embryological structures give rise to the SVC?
Dorsal; sensory
Right common cardinal vein and right anterior cardinal vein
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
Failure to recanalize; 21

31. What causes a patent foramen ovale?
Excessive resorption of septum primum or secondum (or both)
1st branchial arch
Failure of the urachus to obliterate
Apical ectodermal ridge

32. What separates the ant 1/3 and post 2/3 of tongue?
Upper 1/3; urogenital sinus
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)
Foramen cecum and terminal sulus
Neural crest cells

33. What does DHT turn the urogenital folds into? estrogen?
Arnold chiari; syringomyelia
Ventral shaft of penis (penile urethra); labia minora
Arches 3 and 4
After; extrinsic

34. Most myelomeningoceles present in the _______ region
lumbosacral
5th
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum

35. what closes the ductus arteriousus?
Amniotic cavity and yolk sac
3rd pouch
Increase in oxygen concentration which decreases prostaglandin concentration
Polyhydramnios

36. What is the 'fetal period'- ie When is it?
Week 8
Week 3-8
From endocardial cushions (ventral and dorsal meet each other)
Diencephalon

37. What does the ductus arteriosus shunt blood away from - to where? What is its remnant?
Lithium
28 week onward
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
Mesoderm; nucleous pulposos

38. What do the 2nd through 4th clefts of the branchial apparatus correlate to?
Primitive ventricle
Temporary cervical sinus
Muscles and arteries
Deformation

39. What is the defect in spina bifida occulta? is there any structural herniation? where on the spinal cord is it usually seen?
Failure of bony spinal canal to fuse; no; lower vertebral levels
can make cells
Cytotrophoblast
Surface ectoderm

40. What type of blood do umbilical arteries carry? From where to where?
Deoxygenated blood; fetal internal iliac arteries to placenta
monoamniotic
Neural crest cells
Maxillary

41. From What embryonic layer does the gut tube derivatives arise (lungs liver - pancreas - parathryroid - thyroid follicular cells - thymus)?
Neural crest cells
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
Endoderm
VSD

42. By what week is the neural tube supposed to be closed? when did it start forming?
Week 4; week 3
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari
Day 6; maintains corpus luteum; 1st trimester
Valproate acid

43. What causes the obstruction in pyloric stenosis? treatment?
Week 3-8
Hypertrophy of muscularis externis of pylorus; surgical incision
Thalidomide; nausea
lumbosacral

44. What teratogen can cause inhibition of intestinal folate absorption and thus neural tube defects?
Mesoderm
Neuroectoderm
Failure to recanalize; 21
Valproate acid

45. Cleft lip is a failure of fusion of ________ and ______.
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric
Maxillary and medial nasal processes
Nutrient and gas exchange
Polyhydramnios

46. In anencephaly you see...
DiGeorge
Ebsteins anomaly; tricuspid atresia
elevated AFP
Excessive resorption of septum primum or secondum (or both)

47. What teratogen can cause an absence of digits amongst other things in the fetus? give an example.
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
3rd pouch
Alkylating agents
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)

48. What role does the placenta have?
Nutrient and gas exchange
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
Deoxygenated blood; fetal internal iliac arteries to placenta
Ectoderm; endoderm

49. 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
Skewed development of AP septum
Cerebellar tonsillar herniation through foramen magnum
Base of limbs in the zone of polarizing activity; ant - post

50. What are the three regions of the brain (in order of cranial to caudal)?
Neural crest cells
Wolffian; mullerian
All or none
Prosencephalon - mesencephalon - rhombencephalon