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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 layer is the epiblast? hypoblast?
Ectoderm; endoderm
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility
Branchial arch 2
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast

2. From What embryonic layer does the epidermis arise?
Neural crest cells
Surface ectoderm
Oligohydramnios
Absent cerebellar vermis; cystic enlargement of 4th ventricle

3. From What embryonic layer does the gut tube epithelium arise?
Amniotic epithelium
Hypospadias
Surface ectoderm
Endoderm

4. which tracts are damaged first in syringomelia? What tract is preserved?
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric
Spinothalamic first
Arches 3 and 4
Female; paramesonephric; mesonephric

5. When does hCG secretion take place? with what event?
Day 6; with implantation
Reicherts cartilage: Stapes - Styloid process - Lesser horn of hyloid - Stylohyoid ligament and CN VII
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
Base of limbs in the zone of polarizing activity; ant - post

6. What type of blood do umbilical veins carry? From where to where?
Oxygenated; placenta to fetus (IVC)
Ectoderm
3rd and 4th arches
Cerebellar tonsillar herniation through foramen magnum

7. From What embryonic layer is the vagina from? testes? ovaries?
Ectoderm
Hepatic circulation; ligamentum venosum
Mesoderm
Week 3; primitive streak formation from the epiblast makes the three layers

8. What embryologic structure gives rise to the smooth outflow tracts of the ventricles? what else does it give rise to?
Neural crest cells
Dorsal; faulty positioning of genital tubercle
Bulbos Cordis; right ventricle entirely
3rd pouch

9. How many components are there to the placenta? What are they called?
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
Week 8
Fetal and maternal
ACE inhibitors - HCTZ

10. What causes the transposition of the great vessels? What does it result in?
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
Embryonic period; 1st trimester
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems

11. What is holoprosencephaly? what eye disorder does it result in?
Endometrium
Failure of bony spinal canal to fuse; no; lower vertebral levels
Cytotrophoblast and synctiotrophoblast
Decreased separation of hemispheres across midline; cyclopia

12. From What embryonic layer does the spinal cord arise?
All or none
Excessive resorption of septum primum or secondum (or both)
monoamniotic
Neuroectoderm

13. Name a syndrome cleft palate is often seen in
Incomplete; yes
DiGeorge
Urachus/median umbilical ligament; bladder and yolk sac
Indomethacin; blocks PG production

14. What is an arnold chiari II malformation? through what hole does it herniate?
Cerebellar tonsillar herniation through foramen magnum
Neural crest cells
Week 4
All 3

15. What axis is Wnt 7 responsible for developing?
Dorsal ventral axis
Ectoderm
Umbilical - midgut herniates through umbilical ring; SMA
Spinothalamic first

16. Which cranial nerve innervates the motor function of the tongue?
Sperm plus egg
Sonic Hedgehog
XII
1st

17. What does the maternal component of the placenta provide? Where is it derived from?
Dorsal; sensory
Week 4
Nutrient and gas for exchange; endometrium
Apical ectodermal ridge

18. Which branchial arch derivative is obliterated?
Muscles and arteries
5th
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
Mesoderm; nucleous pulposos

19. What are the two components of the fetal component of the placenta?
Cytotrophoblast and synctiotrophoblast
Mesoderm
Upper 1/3; urogenital sinus
Surface ectoderm

20. From what region of the brain does the aqueduct form?
IX; X
3rd pouch
Rhombencephalon
Surface ectoderm

21. What is the prochordal plate?
Found in lateral neck; from no obliteration of 2-4th clefts
External auditory meatus
Deoxygenated blood; fetal internal iliac arteries to placenta
Where the epiblast and hypoblast fuse

22. What is the female remnant of the gubernaculum? male remnant?
Pronephros - mesonephros - metanephros; pronephros; most cranially
VACTERL; OCPs and maternal diabetes
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
Mesoderm

23. What congenital abnormality forms a 'double bubble' on xray?
Amniotic epithelium
Sperm plus egg
Left horn of the sinus venosus
Annular pancrease

24. From What embryonic layer does a craniopharygioma arise?
Surface ectoderm
3rd; proximal part of the internal carotid artery
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
Turners; inferior

25. Which branchial apparatus develops into the superior parathyroids?
Diencephalon
Fallopian tube - uterus - upper 1/3 of vagina
4th pouch
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

26. From where does the signal come from to suppress paramesonephric ducts? what stimulates development of the mesonephric ducts?
Germinal matrix hemorrhage
Neural crest cells
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
blood entering the RA

27. Which is more common - epispadias or hypospadias?
Hypospadias
Rhombencephalon
Bulbos Cordis; right ventricle entirely
Failure to recanalize; 21

28. What is the initial step to interventricular septum development? is it complete?
DHT; estrogen
Muscular ventricular septum; no
Pataus; fetal alcohol syndrome
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells

29. What does the ductus arteriosus shunt blood away from - to where? What is its remnant?
3
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
Mesoderm; 3 week
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood

30. From what aortic arch does the common carotid artery arise? what else arises from this arch?
lumbosacral
Oxygenated; placenta to fetus (IVC)
3rd; proximal part of the internal carotid artery
LH

31. From What embryonic layer does the sensory organs of the ear arise?
Neuroectoderm
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
Week 2; bilaminar disk; epiblast and hypoblast
Surface ectoderm

32. What teratogen can cause IUGR and ADHD in a fetus? what else can this teratogen cause?
Spinothalamic first
Oligohydramnios
Synctiotrophoblast; outer; no
Nicotine; preterm labor

33. which teratogen can cause Ebsteins anomaly in the fetus?
Branchial arch 2
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
First branchial pouch
Lithium

34. Where is the apical ectodermal ridge?
Bones - cartilage - and nerves
arnold chiari associated with thoraclumbar myelomeningocele
Thickened ectoderm at end of each developing limb
Cytotrophoblast

35. What is germinal matrix hemorrhage associated with?
Left horn of the sinus venosus
IX; X
Respiratory distress syndrome
Nicotine; preterm labor

36. From What do the embryoblast and trophoblast form from? What does the embryoblast split into? the trophoblast?
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast
Mid gut to yolk sac; omphalomesenteric duct; 7th week
Neuroectoderm
Bulbos Cordis; right ventricle entirely

37. what closes the interventricular foramen?
From teh lung;blood from IVC in RA to LA; fossa ovalis
Physiologic incomplete muscular ventricular septum
Sperm plus egg
Neural crest cells

38. What components do the neural crest cells of the branchial arches give rise to?
Renal artery stenosis;
Bones - cartilage - and nerves
Dorsal; sensory
28 week onward

39. What is meckel's diverticulum? What is it associated with? What does that cause?
Absent cerebellar vermis; cystic enlargement of 4th ventricle
1st
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
Duodenum to transverse colon; distal transverse colon to rectum

40. What is annular pancreas associated with in infants?
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
Week 3; primitive streak formation from the epiblast makes the three layers
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
V3; VII

41. The spinal cord is made from...
Week 8
Neuroectoderm
Mesoderm
T neuroectoderm

42. From where to Where is the foregut derivative? midgut? hindgut?
septum primum and/or secundum
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum
LH
Fetal alcohol syndrome; mental retardation

43. what bone/cartilage are derived from branchial arch 4-6?
Nutrient and gas for exchange; endometrium
Upper 1/3; urogenital sinus
Decreased pulmonary resistance in the pulmonary vasculature
Thyroid - cricoid - arytenoids - corniculate cuneiform

44. From What embryonic layer does the skin dermis arise?
Incomplete; yes
Neural crest cells
Mesoderm
Aortic arch (from left side); right subclavian (on the right)

45. Where is sonic hedgehog gene produced? What axis is it responsible in patterning?
Reicherts cartilage: Stapes - Styloid process - Lesser horn of hyloid - Stylohyoid ligament and CN VII
Base of limbs in the zone of polarizing activity; ant - post
Prosencephalon
Allantois

46. What connects the thyroid to the tongue? when happens if it doesnt obliterate?
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
Midgut; 10th week
Apical ectodermal ridge
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct

47. What do the groove/clefts of the branchial apparatus correlate to?
Tetracyclines
Ectoderm
Aortic arch (from left side); right subclavian (on the right)
Tunica vaginalis not fully fused

48. what junction is the last to canalize? what implications does this have down the line?
External auditory meatus
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari
Occiptal

49. From where do the three different kidneys come from? Which is the earliest one? is it located most cranially or caudally?
Pronephros - mesonephros - metanephros; pronephros; most cranially
Dorsal ventral axis
Congenital and chromosomal abnormalities
DiGeorge

50. What does the ductus venosus shunt blood away from? What is its remnant?
Before getting pregnant!
Hepatic circulation; ligamentum venosum
T neuroectoderm
Mesoderm; 3 week