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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 causes the increase in left atrial pressure to close the fossa ovale?
Decreased pulmonary resistance in the pulmonary vasculature
After; extrinsic
Mesoderm
Pulm art (prox) and ductus arteriosus

2. What do membranous interventricular septal defect cause? What does this lead to?
Initial left to right shunting - then switches
StyloPharyngeus
Neural crest cells
Week 3; primitive streak formation from the epiblast makes the three layers

3. Which branchial derivative accounts for taste in the ant 2/3?
Prenatal and perinatal
Branchial arch 2
Aminoglycosides
Week 3-8

4. From What embryonic layer does bone of the skulls arise?
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
4th week
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Neural crest cells

5. What can vit A in excess cause in the fetus?
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
Annular pancrease
Lots - cleft palate/lip
Week 8

6. When is most important to take folic acid to prevent neural tube defects?
mesoderm
Before getting pregnant!
Bone/cartilage and nerves
Synctiotrophoblast

7. From What embryonic layer are the serous linings of the body cavities from? for ex - peritoneum?
Temporary cervical sinus
...
Fallopian tube - uterus - upper 1/3 of vagina
Surface ectoderm

8. What does the foramen ovale shunt blood from - to where? What is its remnant?
ACE inhibitors - HCTZ
Dorsal ventral axis
From teh lung;blood from IVC in RA to LA; fossa ovalis
DiGeorge

9. What does the first cleft/groove of the branchial apparatus develop into?
Tetracyclines
Week 4
OCPS and maternal diabetes
External auditory meatus

10. What axis is Wnt 7 responsible for developing?
Dorsal ventral axis
Prosencephalon - mesencephalon - rhombencephalon
Neural crest cells
Dorsal; sensory

11. which genital embryology is default? From what duct? what duct degenerates without signal to stay?
Female; paramesonephric; mesonephric
Neuroectoderm
Mesonephros; male genital system
septum primum and/or secundum

12. What teratogen can cause an absence of digits amongst other things in the fetus? give an example.
Base of limbs in the zone of polarizing activity; ant - post
Alkylating agents
A vitelline fistula - failure of vitelline duct to close
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

13. What axis does the alar plate form? what neural system does it become?
28 week onward
Endocardial cushions
Dorsal; sensory
Partial AP septum development; one large vessel leaves the heart - Right to left shunt

14. What hormones are in charge of external genitalia development in the fetus? (in both male and female)
Left horn of the sinus venosus
DHT; estrogen
Alkylating agents
2nd; 2nd

15. When does the notochord form? and When does the neural plate form?
Synctiotrophoblast; outer; no
Mesoderm; 3 week
Vascular accident intra uterine; apple peel atresia
Mesonephros; male genital system

16. From What embryonic layer is aorticopulmonary septum from ?
Nutrient and gas for exchange; endometrium
Neural crest cells
Urachus/median umbilical ligament; bladder and yolk sac
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks

17. From what are the umbilical arteries and veins derived from?
Allantois
Decreased separation of hemispheres across midline; cyclopia
Ectoderm; endoderm
Congenital and chromosomal abnormalities

18. What is a teratogen that causes Ebsteins anomaly? What is ebsteins anomaly?

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19. What is the 'fetal period'- ie When is it?
is no longer intact
Week 8
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
3

20. What separates the ant 1/3 and post 2/3 of tongue?
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
Pronephros - mesonephros - metanephros; pronephros; most cranially
Foramen cecum and terminal sulus
After; extrinsic

21. The inner layer of the chorionic villi...
4th/5th branchial pouches
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari
OCPS and maternal diabetes
can make cells

22. From What embryonic layer do the ANS arise?
Week 3-8
Week 4
Midgut; 10th week
Neural crest cells

23. What does the maternal component of the placenta provide? Where is it derived from?
Nutrient and gas for exchange; endometrium
Neural crest cells
Mesoderm
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)

24. Septum primum (patent foramen oval) caused by excessive resorption of...
Dorsal; faulty positioning of genital tubercle
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
septum primum and/or secundum
Surface ectoderm

25. From What embryonic layer does the retina arise?
Fetal alcohol syndrome; mental retardation
Neuroectoderm
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
4th/5th branchial pouches

26. What artery is derived branchial (aortic) arch 2?
Synctiotrophoblast; outer; no
Stapedius and hyoid artery
arnold chiari associated with thoraclumbar myelomeningocele
3

27. What are markers for neural tube defects in the amniotic cavity? CSF?
Increased AFP and acetycholinesterase (not ACh!) in CSF
Endoderm
Prosencephalon - mesencephalon - rhombencephalon
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain

28. From What embryonic layer is the bladder and urethra from?
Base of limbs in the zone of polarizing activity; ant - post
Mesoderm
Nutrient and gas exchange
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells

29. what other facial defect other than cyclopia is associated with holoprosencephaly?
Neural crest cells
Mesoderm; epiblast
Cleft lip/palate
Outgrowth of mesonephric as ureteric bud; most caudal

30. By what week is the neural tube supposed to be closed? when did it start forming?
External auditory meatus
Surface ectoderm
Week 4; week 3
Truncus arteriosus; pulmonary trunk

31. What part of the gut rotates around the SMA? and At what point?
Synctiotrophoblast; outer; no
Ventral bud
Midgut; 10th week
Medial palatine processes

32. WithIn what week does gastrulation occur? What is gastrulation?
Hemorrhage - bone deformities
Failure of the urachus to obliterate
Week 3; primitive streak formation from the epiblast makes the three layers
Arches 3 and 4

33. What is contained in the umbilical cord?
Mid gut to yolk sac; omphalomesenteric duct; 7th week
Lithium
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
Found in lateral neck; from no obliteration of 2-4th clefts

34. From What embryonic layer does connective tissue and muscle arise?
Mesoderm
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility
3rd; proximal part of the internal carotid artery
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)

35. what closes the interventricular foramen?
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Bulbos Cordis; right ventricle entirely
Physiologic incomplete muscular ventricular septum
hypertrophy

36. Where is the apical ectodermal ridge?
Thickened ectoderm at end of each developing limb
Week 3; primitive streak formation from the epiblast makes the three layers
Surface ectoderm
Day 6; maintains corpus luteum; 1st trimester

37. Which CN accounts for the anterior 2/3 of the tongues sensation and pain? how about taste?
pyloric stenosis
V3; VII
80%
Scrotum; labia majora

38. what bone/cartilage and nerves are derived from branchial arch 2?
Epiblast
Reicherts cartilage: Stapes - Styloid process - Lesser horn of hyloid - Stylohyoid ligament and CN VII
Cerebral hemisphere - thalami
Neural crest cells

39. By when are the neuropores supposed to fuse?
4th week
Week 3-8
Mid gut to yolk sac; omphalomesenteric duct; 7th week
Nutrient and gas exchange

40. What effect does warfarin have on the fetus?
First branchial pouch
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Bulbos Cordis; right ventricle entirely
Hemorrhage - bone deformities

41. When does organogenesis occur?
Week 3-8
Before getting pregnant!
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
2nd; 2nd

42. As a horseshoe kidney ascends during kidney development - What do they get trapped under?
IMA
Temporary cervical sinus
Foramen cecum and terminal sulus
mesoderm

43. What is the mnueomonic for the mesodermal defects? What does it stand for?
Neuroectoderm
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects
Week 10-12; end of 1st trimester
All 3

44. When does the neural tube form and From what does it form?
Fluid filled syrinx causes expansion and degeneration of cord tracts
Neural plate; closes by week 4
When left to right shunting switching to right to left shunting
Surface ectoderm

45. For what reason do hypospadias need to be fixed?
Foramen cecum and terminal sulus
Prevent recurrent UTIs
elevated AFP
4th/5th branchial pouches

46. What does the RET gene encode? what neoplasias is it associated with?
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)
is no longer intact
Fluid filled syrinx causes expansion and degeneration of cord tracts
Week 2; bilaminar disk; epiblast and hypoblast

47. From What embryonic layer does the oligodendrocytes arise?
Common carotid and internal carotid
Neuroectoderm
Foregut; dorsal mesentery (mesodermal)
Week 2; bilaminar disk; epiblast and hypoblast

48. what muscles are derived from branchial arch 6? CN?
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)
Outgrowth of mesonephric as ureteric bud; most caudal
Neural crest cells
Ventral bud

49. What is the homeobox gene responsible in developing? (What axis)
Amniotic epithelium
Neuroectoderm
Neural crest cells
Cranio - caudal; segmental

50. With the first breath the infant take - pulmonary vasculature resistance _______ which causes an increase in left atrial pressure
Before getting pregnant!
Decreases
Temporary cervical sinus
External auditory meatus