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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 germ layer correlates with the branchial pouches?
Endoderm
Ebsteins anomaly; tricuspid atresia
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
4th/5th branchial pouches

2. Which branchial apparatus makes the external auditory meatus?
Congenital and chromosomal abnormalities
1st cleft/groove (Ectoderm)
Cranio - caudal; segmental
Ionizing

3. What arises from the fourth aortic arch?
Pataus; fetal alcohol syndrome
Aortic arch (from left side); right subclavian (on the right)
When left to right shunting switching to right to left shunting
...

4. In order to survive tricuspid atresia - What do you need?
Rhombencephalon
Muscular ventricular septum; no
Right horn of the SV
VSD

5. What causes urine discharge from the umbilicus?
Failure of the urachus to obliterate
Fluid filled syrinx causes expansion and degeneration of cord tracts
Foramen cecum and terminal sulus
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3

6. ______________ is associated with ventral curvature of the penis
hypospadias
mesoderm
Mesoderm; nucleous pulposos
Fetal and maternal

7. From what aortic arch does the common carotid artery arise? what else arises from this arch?
3rd; proximal part of the internal carotid artery
Week 3; primitive streak formation from the epiblast makes the three layers
Aminoglycosides
Diencephalon

8. What is the leading cause of birth defects in the US? what else is this perpetrator the leading cause of?
Mesoderm
Renal artery stenosis;
Neuroectoderm
Fetal alcohol syndrome; mental retardation

9. What does the ductus venosus shunt blood away from? What is its remnant?
6th aortic arch
Hepatic circulation; ligamentum venosum
Epispadias
Membrane - all 3 from 1st appartus

10. What happens in pancreas divisum? what results?
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3
Neuroectoderm
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis

11. From where did a branchial cleft cyst arise if it found?
VSD
Found in lateral neck; from no obliteration of 2-4th clefts
Scrotum; labia majora
Oligohydramnios

12. What is associated with only one umbilical artery?
Congenital and chromosomal abnormalities
Cerebral hemisphere - thalami
Rhombencephalon
From endocardial cushions (ventral and dorsal meet each other)

13. From What embryonic layer does the sensory organs of the ear arise?
Surface ectoderm
not covered
Endometrium
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain

14. what chemo drugs can cause neural tube defects in the fetus?
Folate antagonists
Cytotrophoblast
Yolk sac; 3rd week
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects

15. What is annular pancreas associated with in infants?
2; 1
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
Increase in oxygen concentration which decreases prostaglandin concentration
Allantois

16. What part of the gut rotates around the SMA? and At what point?
Midgut; 10th week
Mesoderm
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus
Common carotid and internal carotid

17. Weeks _______ erythropoiesis takes place in the liver
6-30
Decreases
Dorsal; faulty positioning of genital tubercle
Ventral; failure of urogenital folds to close

18. From What embryonic layer does the epidermis arise?
Surface ectoderm
Partial AP septum development; one large vessel leaves the heart - Right to left shunt
Hemorrhage - bone deformities
Pataus; fetal alcohol syndrome

19. What results in annular pancreas? How does it happen?
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects
Ampulla
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum

20. What axis is Wnt 7 responsible for developing?
Dorsal ventral axis
Neuroectoderm
Thalidomide; nausea
1st

21. What artery is derived branchial (aortic) arch 4?
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Cytotrophoblast
Aortic arch and prox part of subclavian
Branchial arch 2

22. Most myelomeningoceles present in the _______ region
Week 4; week 3
...
lumbosacral
Stapedius and hyoid artery

23. What does the RET gene encode? what neoplasias is it associated with?
Endoderm
Endoderm
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)
Mesoderm

24. From What embryonic layer does the epithelial linings of the oral cavity arise?
Prosencephalon - mesencephalon - rhombencephalon
Surface ectoderm
Female; paramesonephric; mesonephric
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum

25. Which branchial derivative creates the middle ear cavity - eustachian tube and mastoid air cells?
Surface ectoderm
XII
Endoderm
First branchial pouch

26. What is the memranous interventricular formaen made from?
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
Week 3; primitive streak formation from the epiblast makes the three layers
DHT; estrogen
Neuroectoderm

27. What is the primitive streak? From what layer does it form?
Mesoderm; epiblast
2; 1
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
3rd and 4th arches

28. is epispadias or hypospadias associated with exstrophy of the bladder?
mesoderm
Fluid filled syrinx causes expansion and degeneration of cord tracts
Nicotine; preterm labor
Epispadias

29. What are the three results of having pathology in the aorticopulmonary septum?
3rd and 4th arches
From teh lung;blood from IVC in RA to LA; fossa ovalis
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)
Neuroectoderm

30. How many umbilical arteries are there? How many umbilical veins?
Synctiotrophoblast
4th arch; 6th arch
A vitelline fistula - failure of vitelline duct to close
2; 1

31. What embryologic structure provides the aorticpulmonary septum?
Neural crest migration - they then cause spiral
Mesoderm
Foregut; dorsal mesentery (mesodermal)
From teh lung;blood from IVC in RA to LA; fossa ovalis

32. When is most important to take folic acid to prevent neural tube defects?
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
Dorsal; faulty positioning of genital tubercle
Before getting pregnant!
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast

33. From What embryonic layer does the thyroid follicular cells arise?
Branchial arch 2
Cleft lip/palate
Endoderm
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck

34. From What embryonic layer does a craniopharygioma arise?
After; extrinsic
Tongue
Ventral; failure of urogenital folds to close
Surface ectoderm

35. The notochord is...
...
Ventral bud
Sperm plus egg
mesoderm

36. What embryological structure gives rise to the coronary sinus?
Wolffian; mullerian
Myelencephalon
Left horn of the sinus venosus
Ionizing

37. What causes persistent Truncus Arteriosus? What does it result in?
Initial left to right shunting - then switches
Deformation
3rd and 4th arches
Partial AP septum development; one large vessel leaves the heart - Right to left shunt

38. With the first breath the infant take - pulmonary vasculature resistance _______ which causes an increase in left atrial pressure
Neural crest cells
Metencephalon; cerebellum
DES
Decreases

39. Cleft lip is a failure of formation of the...
Duodenum to transverse colon; distal transverse colon to rectum
Excessive resorption of septum primum or secondum (or both)
Fetal and maternal
primary palate

40. When does hCG secretion take place? with what event?
Day 6; with implantation
Membrane - all 3 from 1st appartus
Pulm art (prox) and ductus arteriosus
Thickened ectoderm at end of each developing limb

41. From where is the allantois formed? During what week?
4th arch; 6th arch
Yolk sac; 3rd week
Cleft lip/palate
Cerebellar tonsillar herniation through foramen magnum

42. What embryological structure gives rise to the smooth part of the right atrium?
2nd; 2nd
Ventral shaft of penis (penile urethra); labia minora
Failure of the urachus to obliterate
Right horn of the SV

43. What is the initial step to interventricular septum development? is it complete?
blood entering the RA
Muscular ventricular septum; no
Persistent connection between amniotic cavity and spinal canal; low folic acid
elevated AFP

44. From What embryonic lare are the odontoblasts from?
Neural crest cells
Endoderm - floor of primitive pharynx
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct

45. which genital embryology is default? From what duct? what duct degenerates without signal to stay?
Bones - cartilage - and nerves
Female; paramesonephric; mesonephric
Pulm art (prox) and ductus arteriosus
Found in lateral neck; from no obliteration of 2-4th clefts

46. When does the neural tube form and From what does it form?
DiGeorge
Neural plate; closes by week 4
Ebsteins anomaly; tricuspid atresia
Alkylating agents

47. which posterior fossa malformation results in aqueductal stenosis and hydrocephaly? what other spinal cord lesion does this malformation present with?
6th aortic arch
Mesoderm
Arnold chiari; syringomyelia
Neuroectoderm

48. Name a syndrome cleft palate is often seen in
Ectoderm
Prevent recurrent UTIs
DiGeorge
4th week

49. What are two common findings in pyloric stenosis?
elevated AFP
Endocardial cushions
6-30
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks

50. What does the maternal component of the placenta provide? Where is it derived from?
Rhombencephalon
Nutrient and gas for exchange; endometrium
Arches 3 and 4
Bone/cartilage and nerves