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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 tetralogy of Fallot?
Excessive resorption of septum primum or secondum (or both)
Where the epiblast and hypoblast fuse
Skewed development of AP septum
Surface ectoderm

2. From what region do the thalami form?
Week 2; bilaminar disk; epiblast and hypoblast
LH
Diencephalon
Sonic Hedgehog

3. What are the neural crest cells and where do they come form? where do they go?
Incomplete; yes
They are the edge of neural plate folding; all over the body
Rhombencephalon
No more umbilical circulation emptying into RA

4. What hormones are in charge of external genitalia development in the fetus? (in both male and female)
Synctiotrophoblast
DHT; estrogen
pyloric stenosis
Decreased pulmonary resistance in the pulmonary vasculature

5. From where is the allantois formed? During what week?
...
Yolk sac; 3rd week
Folate antagonists
Lacunae in between the chorionic villi

6. What are the three results of having pathology in the aorticopulmonary septum?
Neuroectoderm
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)
Membrane - all 3 from 1st appartus
DHT; estrogen

7. What effect does warfarin have on the fetus?
Hemorrhage - bone deformities
Neural crest cells
Neural crest cells
Mesoderm

8. What do the groove/clefts of the branchial apparatus correlate to?
lumbosacral
Bone/cartilage and nerves
Ectoderm
Diencephalon

9. From What embryonic layer does bone arise ?
Mesoderm
not covered
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation

10. What artery is derived branchial (aortic) arch 1?
Surface ectoderm
Maxillary
Pataus; fetal alcohol syndrome
Sperm plus egg

11. From What embryonic layer does the thyroid follicular cells arise?
Persistent connection between amniotic cavity and spinal canal; low folic acid
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
Endoderm
Cerebellar tonsillar herniation through foramen magnum

12. As a horseshoe kidney ascends during kidney development - What do they get trapped under?
Increased AFP and acetycholinesterase (not ACh!) in CSF
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)
Deformation
IMA

13. Cleft lip is a failure of formation of the...
Decreases
Rhombencephalon
primary palate
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3

14. What does the midgut form? hindgut?
Partial AP septum development; one large vessel leaves the heart - Right to left shunt
Duodenum to transverse colon; distal transverse colon to rectum
Mesoderm; epiblast
Mesoderm

15. From What embryonic layer does bone of the skulls arise?
Neural crest cells
Mesoderm
Maternally derived; meconium
Deformation

16. To what germ layer does the branchial pouches correlate to?
Neural crest migration - they then cause spiral
Endoderm
Week 4
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs

17. From What embryonic layer are the serous linings of the body cavities from? for ex - peritoneum?
Ectoderm
DiGeorge
...
When left to right shunting switching to right to left shunting

18. what results if they dont? What can increase the risks of this?
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility
Persistent connection between amniotic cavity and spinal canal; low folic acid
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
Muscles and arteries

19. what other facial defect other than cyclopia is associated with holoprosencephaly?
Failure of bony spinal canal to fuse; no; lower vertebral levels
Mesoderm
Temporary cervical sinus
Cleft lip/palate

20. From What embryonic layer does the parathyroid arise ?
Mesoderm; epiblast
Obliterated
Endoderm
hypertrophy

21. What are the clinical symptoms that present with syringomelia?
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Medial palatine processes
Bones - cartilage - and nerves
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation

22. What congenital abnormality forms a 'double bubble' on xray?
Week 4
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility
Arnold chiari; syringomyelia
Annular pancrease

23. From what aortic arch does the first part of the maxillary artery arise?
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule
1st
Valproate acid
Endoderm

24. From where does the medulla form?
not covered
3rd pouch
Myelencephalon
Allantois

25. what bone/cartilage and nerves are derived from branchial arch 3?
elevated AFP
Week 4
Dorsal and ventral buds
Greater horn of hyoid; CN IX (styloPharyngeus)

26. What is the female remnant of the gubernaculum? male remnant?
Endometrium
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
hypospadias
Spinothalamic first

27. What does the mullerian duct develop into? wollffian?
Surface ectoderm
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Fallopian tube - uterus - upper 1/3 of vagina
Common carotid and internal carotid

28. Cleft palate is a failure of formation of the...
Mid gut to yolk sac; omphalomesenteric duct; 7th week
Telencephalon
A vitelline fistula - failure of vitelline duct to close
secondary palate

29. What is the allantois become? What is this duct connected to ( on both ends)?
Prosencephalon
not covered
is no longer intact
Urachus/median umbilical ligament; bladder and yolk sac

30. what structures are the derivatives of the neural crest cells in branchial arches?
Bone/cartilage and nerves
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
Ampulla
Surface ectoderm

31. What are the two types of posterior fossa malformations? which one results in a hindbrain crowding? and which results in an enlarged posterior fossa? which one is associated with syringomelia?
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric
4th arch; 6th arch
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari
Thickened ectoderm at end of each developing limb

32. What teratogen can cause vaginal clear cell adenocarcinoma in the fetus?
Endoderm
Aortic arch (from left side); right subclavian (on the right)
Surface ectoderm
DES

33. Which CN allows for taste and sensation in the posterior 1/3 of the tongue? how about the very back ?
Aortic arch (from left side); right subclavian (on the right)
IX; X
Sperm plus egg
Mesonephros; male genital system

34. Where is the decidua basalis derived from?
Upper 1/3; urogenital sinus
Dorsal and ventral buds
Endometrium
Mid gut to yolk sac; omphalomesenteric duct; 7th week

35. Which branchial derivative creates the epithelial lining of the palatine tonsils?
2nd pouch
Cerebellar tonsillar herniation through foramen magnum
Telencephalon
Muscular ventricular septum; no

36. What three layers form during gastrulation? From What do they form? and what week does gastrulation occur?
Neuroectoderm
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts

37. From where is the pancreas derived? the spleen?
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Surface ectoderm
2; 1
Foregut; dorsal mesentery (mesodermal)

38. When does hCG secretion take place? with what event?
Day 6; with implantation
External auditory meatus
Sperm plus egg
Mid gut to yolk sac; omphalomesenteric duct; 7th week

39. From What embryonic layer does connective tissue and muscle arise?
Mesoderm
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
3rd; proximal part of the internal carotid artery
6-30

40. What embryonic structure gives rise to the ascending aorta? what else does it give rise to?
Thalidomide; nausea
Truncus arteriosus; pulmonary trunk
Tunica vaginalis not fully fused
Foramen cecum and terminal sulus

41. what happens in hydrocele?
Mental retardation - holoprosencephaly - facial features - fistulas
Prenatal and perinatal
Tunica vaginalis not fully fused
Nutrient and gas for exchange; endometrium

42. What does the ductus venosus shunt blood away from? What is its remnant?
Epispadias
Decreased separation of hemispheres across midline; cyclopia
Hepatic circulation; ligamentum venosum
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II

43. What is a syrinx? Where is it found in syringomelia? What is it associated with?
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II
Cranio - caudal; segmental
Bone/cartilage and nerves
2nd pouch

44. What teratogens can cause flipper limbs (limb defects)? What is this drug used for?
Thalidomide; nausea
Urachus/median umbilical ligament; bladder and yolk sac
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Branchial arch 2

45. What is the Eisenmeger complex?
Maxillary
No organ in each; agenesis no primordial tissue
hypertrophy
When left to right shunting switching to right to left shunting

46. What embryological structure gives rise to the smooth part of the right atrium?
Prenatal and perinatal
Right horn of the SV
Cranio - caudal; segmental
Week 3-8

47. During what periods do the damages that cerebral palsy causes occur?
DiGeorge
DHT; estrogen
Prenatal and perinatal
6th aortic arch

48. What day is the amnion formed?
3 -4 -6
8
Surface ectoderm
Fallopian tube - uterus - upper 1/3 of vagina

49. What is an example of a syndrome that can cause abnormal neural crest migration and thus CV abnormalities?
DiGeorge
Week 4
Surface ectoderm
Week 8

50. From What embryonic layer does the pineal gland arise?
5th
Neuroectoderm
Surface ectoderm
VACTERL; OCPs and maternal diabetes