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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. From where does pons form from? what else forms from there?
80%
Excessive resorption of septum primum or secondum (or both)
Membrane - all 3 from 1st appartus
Metencephalon; cerebellum

2. WithIn what week does gastrulation occur? What is gastrulation?
Endoderm
After; extrinsic
Increased AFP and acetycholinesterase (not ACh!) in CSF
Week 3; primitive streak formation from the epiblast makes the three layers

3. What does the mullerian duct develop into? wollffian?
After; extrinsic
Fallopian tube - uterus - upper 1/3 of vagina
Mesoderm
3

4. What does the midgut form? hindgut?
Cranio - caudal; segmental
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
Increase in oxygen concentration which decreases prostaglandin concentration
Duodenum to transverse colon; distal transverse colon to rectum

5. In anencephaly you see...
Rhombencephalon
elevated AFP
Failure of the urachus to obliterate
Ionizing

6. Which branchial arch derivative is obliterated?
5th
Rhombencephalon
Mesoderm
Neuroectoderm

7. What embryonic structure gives rise to the ascending aorta? what else does it give rise to?
2; 1
A vitelline fistula - failure of vitelline duct to close
Truncus arteriosus; pulmonary trunk
Mesoderm

8. Which parts of the pancreas contribute to the head - uncinate process and main pancreatic duct?
Dorsal and ventral buds
Neuroectoderm
Failure of the urachus to obliterate
Endoderm

9. During what week do the limbs begin to form?
Ebsteins anomaly; tricuspid atresia
Ventral bud
Week 4
Greater horn of hyoid; CN IX (styloPharyngeus)

10. What is an example of a syndrome that can cause abnormal neural crest migration and thus CV abnormalities?
DiGeorge
28 week onward
Ectoderm; endoderm
not covered

11. From what region do the thalami form?
Week 8
Week 3-8
Neuroectoderm
Diencephalon

12. Which branchial derivative creates the middle ear cavity - eustachian tube and mastoid air cells?
Week 3; primitive streak formation from the epiblast makes the three layers
Wolffian; mullerian
blood entering the RA
First branchial pouch

13. What do the 2nd through 4th clefts of the branchial apparatus correlate to?
Greater horn of hyoid; CN IX (styloPharyngeus)
Amniotic cavity and yolk sac
From teh lung;blood from IVC in RA to LA; fossa ovalis
Temporary cervical sinus

14. What separated myometrium of the uterus from the blastocyst?
Decidual basalis
Hypospadias
elevated AFP
Decreased separation of hemispheres across midline; cyclopia

15. What causes meconium discharge from the umbilicus?
Post. sup wall; luteal phase
A vitelline fistula - failure of vitelline duct to close
Urachus/median umbilical ligament; bladder and yolk sac
Decreased separation of hemispheres across midline; cyclopia

16. What are the clinical symptoms that present with syringomelia?
Initial left to right shunting - then switches
Prosencephalon - mesencephalon - rhombencephalon
Synctiotrophoblast; outer; no
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation

17. What axis is Wnt 7 responsible for developing?
Dorsal ventral axis
Increased AFP and acetycholinesterase (not ACh!) in CSF
Turners; inferior
Pronephros - mesonephros - metanephros; pronephros; most cranially

18. What causes the degeneration of the spinal cord in syringomelia?
Fluid filled syrinx causes expansion and degeneration of cord tracts
A vitelline fistula - failure of vitelline duct to close
Valproate acid
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule

19. which posterior fossa malformation results in aqueductal stenosis and hydrocephaly? what other spinal cord lesion does this malformation present with?
mesodermal
A vitelline fistula - failure of vitelline duct to close
blood entering the RA
Arnold chiari; syringomyelia

20. is epispadias or hypospadias associated with exstrophy of the bladder?
Partial AP septum development; one large vessel leaves the heart - Right to left shunt
Cytotrophoblast
Epispadias
LH

21. What is the Eisenmeger complex?
ACE inhibitors - HCTZ
When left to right shunting switching to right to left shunting
Post. sup wall; luteal phase
Upper 1/3; urogenital sinus

22. Other than not having a brain - what else is a symptom of anencephaly? why? hint: think about amniotic fluid
Polyhydramnios
Bulbos Cordis; right ventricle entirely
Surface ectoderm
3rd and 4th arches

23. During what week does the heart begin to beat?
80%
Week 4
Failure to recanalize; 21
Embryonic period; 1st trimester

24. What embryological structure gives rise to the trabeculated parts of the left and right ventricle?
Endoderm
Primitive ventricle
Maxillary
IX; X

25. What is meckel's diverticulum? What is it associated with? What does that cause?
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
Mesoderm; nucleous pulposos
Primitive atrium

26. Name two endocardial cushion defects.
Ebsteins anomaly; tricuspid atresia
First branchial pouch
Medial palatine processes
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari

27. What causes the increase in left atrial pressure to close the fossa ovale?
Membrane - all 3 from 1st appartus
arnold chiari associated with thoraclumbar myelomeningocele
1st cleft/groove (Ectoderm)
Decreased pulmonary resistance in the pulmonary vasculature

28. To what germ layer does the branchial pouches correlate to?
Oligohydramnios
Mesencephalon
Week 8
Endoderm

29. What hormone is hcG structurally similar too?
ACE inhibitors - HCTZ
LH
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)

30. What gene is produced in the zone of polarizing activity?
Sonic Hedgehog
3rd and 4th arches
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari
Left horn of the sinus venosus

31. How do you differentiate a thyroglossal duct cyst from a persistent cervical sinus?
Neuroectoderm
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
Thalidomide; nausea
Polyhydramnios

32. From What embryonic lare are the odontoblasts from?
Renal artery stenosis;
Neural crest cells
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility
Thyroid - cricoid - arytenoids - corniculate cuneiform

33. What effect does warfarin have on the fetus?
All or none
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum
Prosencephalon
Hemorrhage - bone deformities

34. During what months is the fetus most susceptible to teratogens? What trimester?
Embryonic period; 1st trimester
Aortic arch and prox part of subclavian
Increased AFP and acetycholinesterase (not ACh!) in CSF
Membrane - all 3 from 1st appartus

35. What connects the thyroid to the tongue? when happens if it doesnt obliterate?
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
Lithium
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Mesencephalon

36. What are markers for neural tube defects in the amniotic cavity? CSF?
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Epispadias
Increased AFP and acetycholinesterase (not ACh!) in CSF

37. What is the neural plate and From what does it form?
Stapedius and hyoid artery
Mesoderm; epiblast
1st cleft/groove (Ectoderm)
Ectoderm

38. What is perinauds syndrome?
Renal artery stenosis;
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Ionizing
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility

39. What type of blood do umbilical arteries carry? From where to where?
IMA
Deoxygenated blood; fetal internal iliac arteries to placenta
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
pyloric stenosis

40. What is the primitive streak? From what layer does it form?
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3
Neuroectoderm
Aortic arch (from left side); right subclavian (on the right)
Mesoderm; epiblast

41. What teratogen can cause an absence of digits amongst other things in the fetus? give an example.
3
Truncus arteriosus; pulmonary trunk
Neural crest cells
Alkylating agents

42. By what week is the neural tube supposed to be closed? when did it start forming?
Tetracyclines
Day 6; maintains corpus luteum; 1st trimester
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Week 4; week 3

43. What is the initial step to interventricular septum development? is it complete?
Muscular ventricular septum; no
Decreased pulmonary resistance in the pulmonary vasculature
IX; X
Endoderm

44. What is the difference between agenesis and aplasia?
Mental retardation - holoprosencephaly - facial features - fistulas
Nutrient and gas exchange
No organ in each; agenesis no primordial tissue
Pataus; fetal alcohol syndrome

45. On what side is the abnormal opening in epispadias? What causes it?
Wolffian; mullerian
Dorsal; faulty positioning of genital tubercle
Neuroectoderm
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)

46. Which part of the branchial apparatus makes up membranes?
Surface ectoderm
Thyroid - cricoid - arytenoids - corniculate cuneiform
Ebsteins anomaly; tricuspid atresia
All 3

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

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48. Where is the apical ectodermal ridge?
Increased AFP and acetycholinesterase (not ACh!) in CSF
Surface ectoderm
Post. sup wall; luteal phase
Thickened ectoderm at end of each developing limb

49. Name a syndrome cleft palate is often seen in
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
Cytotrophoblast and synctiotrophoblast
Hypospadias
DiGeorge

50. From What embryonic layer are the serous linings of the body cavities from? for ex - peritoneum?
From endocardial cushions (ventral and dorsal meet each other)
Folate antagonists
...
1st cleft/groove (Ectoderm)