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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 cranial nerve innervates the motor function of the tongue?
XII
Outgrowth of mesonephric as ureteric bud; most caudal
not covered
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood

2. What is germinal matrix hemorrhage associated with?
Vascular accident intra uterine; apple peel atresia
Respiratory distress syndrome
Thalidomide; nausea
Surface ectoderm

3. What is the notochord? What does the notochord later become?
Mesoderm; nucleous pulposos
Mesonephros; male genital system
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
Mesoderm; 3 week

4. is epispadias or hypospadias associated with exstrophy of the bladder?
not covered
Post. sup wall; luteal phase
Medial palatine processes
Epispadias

5. 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?
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
Where the epiblast and hypoblast fuse
Excessive resorption of septum primum or secondum (or both)
Synctiotrophoblast; outer; no

6. On what side is the abnormal opening in epispadias? What causes it?
Persistent connection between amniotic cavity and spinal canal; low folic acid
Dorsal; faulty positioning of genital tubercle
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood

7. From What embryonic layer does the neurohypophysis arise?
Upper 1/3; urogenital sinus
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
not covered
Neuroectoderm

8. What hormones are in charge of external genitalia development in the fetus? (in both male and female)
DHT; estrogen
Prostaglandins
1st
Bone/cartilage and nerves

9. From What embryonic layer does the skin dermis arise?
Mesoderm
Female; paramesonephric; mesonephric
...
Pulm art (prox) and ductus arteriosus

10. what muscles are derived from branchial arch 6? CN?
Occiptal
blood entering the RA
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)
Mesdoerm

11. Blood coming in the umbilical vein is ____ saturated
Week 8
80%
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Endoderm

12. What causes the obstruction in pyloric stenosis? treatment?
Mesoderm
Hypertrophy of muscularis externis of pylorus; surgical incision
Cranio - caudal; segmental
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct

13. What type of radiation is teratogenic ?
Ionizing
Failure to recanalize; 21
External auditory meatus
hypertrophy

14. What does the vitelline duct connect? What is it also known as? when should it obliterate?
Wolffian; mullerian
Mesencephalon
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
Mid gut to yolk sac; omphalomesenteric duct; 7th week

15. From What embryonic layer are the schwann cells from ?
Neuroectoderm
Week 10-12; end of 1st trimester
3rd pouch
Neural crest cells

16. From What embryonic layer do CNS neurons arise?
Ectoderm; endoderm
Tunica vaginalis not fully fused
Surface ectoderm
Neuroectoderm

17. How does annular pancreas present in children?
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
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
Aortic arch (from left side); right subclavian (on the right)
Wolffian; mullerian

18. What is the mcc of renovascular hypertension in children? What does this predispose to?
Ventral; failure of urogenital folds to close
Cerebellar tonsillar herniation through foramen magnum
Renal artery stenosis;
Mesoderm

19. What teratogens can cause renal damage in the fetus?
ACE inhibitors - HCTZ
Scrotum; labia majora
Aminoglycosides
Sperm plus egg

20. What is jejunal - ileal - colonic atresia usually due to? What do you see on x ray?
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)
Neuroectoderm
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Vascular accident intra uterine; apple peel atresia

21. What does the first cleft/groove of the branchial apparatus develop into?
3 -4 -6
Failure of the urachus to obliterate; outpouching of the bladder
External auditory meatus
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus

22. From where does the medulla form?
Right horn of the SV
Ventral ; motor
Myelencephalon
Bone/cartilage and nerves

23. What embryologic structure provides the aorticpulmonary septum?
Synctiotrophoblast; outer; no
Maternally derived; meconium
Neural crest migration - they then cause spiral
All 3

24. From What embryonic layer does the oligodendrocytes arise?
Mesoderm
Hypospadias
Neuroectoderm
Muscular ventricular septum; no

25. what bone/cartilage and nerves are derived from branchial arch 1?
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3
Arnold chiari; syringomyelia
arnold chiari associated with thoraclumbar myelomeningocele
hypospadias

26. What is congenital pharyngocutaneous fistula? and How does it occur?
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
Nutrient and gas for exchange; endometrium
Increased AFP and acetycholinesterase (not ACh!) in CSF
Maxillary and medial nasal processes

27. what invaginates to form the primitive streak?
Epiblast
Epispadias
3
Hypertrophy of muscularis externis of pylorus; surgical incision

28. During what months is the fetus most susceptible to teratogens? What trimester?
blood entering the RA
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
Embryonic period; 1st trimester
Muscles and arteries

29. What part of the gut rotates around the SMA? and At what point?
Wolffian; mullerian
Annular pancrease
Midgut; 10th week
Endoderm

30. From What embryonic layer does the epithelial linings of the oral cavity arise?
DiGeorge
Cerebral hemisphere - thalami
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Surface ectoderm

31. From What embryonic layer does the spinal cord arise?
Prevent recurrent UTIs
Excessive resorption of septum primum or secondum (or both)
Neuroectoderm
Lots - cleft palate/lip

32. What do membranous interventricular septal defect cause? What does this lead to?
Week 10-12; end of 1st trimester
Initial left to right shunting - then switches
4th arch; 6th arch
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain

33. Which branchial apparatus develops into the thymus?
lumbosacral
3rd pouch
Endoderm - floor of primitive pharynx
Valproate acid

34. What is the difference between agenesis and aplasia?
DES
Epiblast
Blind upper esophagus with lower esophagus connected to trachea; cyanosis - choking and vomiting with feeding; air bubble on CXR; polyhydramnios; failure to pass NG tube; pneumonitis
No organ in each; agenesis no primordial tissue

35. WithIn what week does gastrulation occur? What is gastrulation?
Bones - cartilage - and nerves
Week 3; primitive streak formation from the epiblast makes the three layers
Neural crest cells
Germinal matrix hemorrhage

36. which tracts are damaged first in syringomelia? What tract is preserved?
Spinothalamic first
Cleft lip/palate
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)
Tunica vaginalis not fully fused

37. From What embryonic layer does bone of the skulls arise?
6-30
Ventral ; motor
Neural crest cells
Week 3-8

38. What embryological structure gives rise to the trabeculated part of the left and right atrium?
Blind upper esophagus with lower esophagus connected to trachea; cyanosis - choking and vomiting with feeding; air bubble on CXR; polyhydramnios; failure to pass NG tube; pneumonitis
Surface ectoderm
Primitive atrium
Lacunae in between the chorionic villi

39. Where is the apical ectodermal ridge?
Thickened ectoderm at end of each developing limb
Base of limbs in the zone of polarizing activity; ant - post
Fetal and maternal
Ectoderm; endoderm

40. Cleft lip is a failure of fusion of ________ and ______.
Surface ectoderm
Maxillary and medial nasal processes
Turners; inferior
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain

41. From What embryonic layer do the astrocytes arise?
Neuroectoderm
Aminoglycosides
Day 6; with implantation
Branchial arch 2

42. The notochord is...
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)
mesoderm
Hypospadias
Primitive atrium

43. what chemo drugs can cause neural tube defects in the fetus?
Primitive ventricle
Fetal and maternal
Folate antagonists
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule

44. From What embryonic layer is the spleen from?
Right common cardinal vein and right anterior cardinal vein
Epiblast
Mesoderm
Endoderm

45. Where is the FGF gene produced? What is it responsible for - How does it do this?
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
3rd pouch
Right common cardinal vein and right anterior cardinal vein
Wolffian; mullerian

46. What teratogens can cause CN VIII toxicity in the fetus?
They are the edge of neural plate folding; all over the body
Aminoglycosides
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Right horn of the SV

47. From what arches are the neural crest cells that form the aorticpulmonary septum derived?
Neural crest cells
Epiblast
3 -4 -6
Ebsteins anomaly; tricuspid atresia

48. From What embryonic layer is the kidney and the adrenal cortex from?
3rd pouch
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
Mesoderm
Initial left to right shunting - then switches

49. From What embryonic layer does the lens of the eye arise?
Outgrowth of mesonephric as ureteric bud; most caudal
Surface ectoderm
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II
Persistent connection between amniotic cavity and spinal canal; low folic acid

50. Which part of the chorionic villi can make cells?
Cytotrophoblast
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Synctiotrophoblast; outer; no
Thickened ectoderm at end of each developing limb