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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 muscles are derived from branchial arch 4? CN?
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
Indomethacin; blocks PG production
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
Neural crest cells

2. what muscles are derived from branchial arch 3?
1st cleft/groove (Ectoderm)
Increase in oxygen concentration which decreases prostaglandin concentration
StyloPharyngeus
Wolffian; mullerian

3. What embryological structures give rise to the SVC?
Decreased pulmonary resistance in the pulmonary vasculature
Right common cardinal vein and right anterior cardinal vein
Thyroid - cricoid - arytenoids - corniculate cuneiform
Metencephalon; cerebellum

4. At what week does the fetus look like a baby?
Week 8
Ectoderm; endoderm
Ventral bud
Absent cerebellar vermis; cystic enlargement of 4th ventricle

5. What layer is the epiblast? hypoblast?
mesodermal
mesoderm
Ectoderm; endoderm
Common carotid and internal carotid

6. From What embryonic layer do the parafollicular cells of the thyroid arise?
Neural crest cells
Midgut; 10th week
A vitelline fistula - failure of vitelline duct to close
Decidual basalis

7. From What embryonic layer is the bladder and urethra from?
4th pouch
Mesoderm
Neural crest cells
Synctiotrophoblast; outer; no

8. What is the effect of teratogens after week 8?
Dorsal ventral axis
Mesoderm
Deformation
Cytotrophoblast

9. What artery is derived branchial (aortic) arch 6?
Pulm art (prox) and ductus arteriosus
VACTERL; OCPs and maternal diabetes
IMA
Neural crest cells

10. From What embryonic layer are the melanocytes from?
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Pronephros - mesonephros - metanephros; pronephros; most cranially
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
Neural crest cells

11. What surrounds the umbilical cord?
Initial left to right shunting - then switches
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
Surface ectoderm
Amniotic epithelium

12. From What embryonic layer does the inner arise?
Neural crest cells
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
...
Ectoderm

13. Pyloric stenosis is characterized by _____________ of muscularis externis in the sphincter
Aortic arch and prox part of subclavian
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
hypertrophy
Branchial arch 2

14. What is the 'fetal period'- ie When is it?
Common carotid and internal carotid
Failure of the urachus to obliterate
Week 8
XII

15. What embryological structure gives rise to the trabeculated parts of the left and right ventricle?
Primitive ventricle
can make cells
Turners; inferior
DES

16. Where is the apical ectodermal ridge?
...
Thickened ectoderm at end of each developing limb
Lacunae in between the chorionic villi
Embryonic period; 1st trimester

17. What type of blood do umbilical arteries carry? From where to where?
Neuroectoderm
...
IX; X
Deoxygenated blood; fetal internal iliac arteries to placenta

18. When does the blastocyst split into two disks? What is this disk called? What are the two germ layers called?
Maxillary
Week 2; bilaminar disk; epiblast and hypoblast
Mesencephalon
Week 4; week 3

19. What does the RET gene encode? what neoplasias is it associated with?
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
Cranio - caudal; segmental
Week 3-8
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)

20. What two cavities also form during the second week?
Amniotic cavity and yolk sac
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Mesoderm
Scrotum; labia majora

21. What are two common findings in pyloric stenosis?
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
80%
Temporary cervical sinus
Where the epiblast and hypoblast fuse

22. What are the two components of the placenta? From What do they form? which one secreted hcG?
Surface ectoderm
StyloPharyngeus
hypospadias
...

23. From What embryonic layer does bone of the skulls arise?
Neural crest cells
Diencephalon
Truncus arteriosus; pulmonary trunk
VSD

24. Where does fertilization occur?
3 -4 -6
T neuroectoderm
DiGeorge
Ampulla

25. What causes the transposition of the great vessels? What does it result in?
Skewed development of AP septum
can make cells
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
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems

26. what results if they dont? What can increase the risks of this?
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Hypertrophy of muscularis externis of pylorus; surgical incision
Week 4; week 3
Persistent connection between amniotic cavity and spinal canal; low folic acid

27. Where is Wnt 7 gene produced?
Apical ectodermal ridge
Aminoglycosides
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
hypertrophy

28. From What embryonic layer does a craniopharygioma arise?
mesodermal
Surface ectoderm
Telencephalon
Neural plate; closes by week 4

29. From What embryonic layer is aorticopulmonary septum from ?
Rhombencephalon
Neural crest cells
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari
Indomethacin; blocks PG production

30. From what germ layer does the primitive heart tube arise?
Surface ectoderm
Decreased pulmonary resistance in the pulmonary vasculature
Mesoderm
Muscular ventricular septum; no

31. What embryological structure gives rise to the smooth part of the right atrium?
Right horn of the SV
arnold chiari associated with thoraclumbar myelomeningocele
Membrane - all 3 from 1st appartus
First branchial pouch

32. What is annular pancreas associated with in infants?
Cleft lip/palate
Cytotrophoblast
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum

33. What secretes hCG?
Allantois
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
Turners; inferior
Synctiotrophoblast

34. Which cranial nerve innervates the motor function of the tongue?
StyloPharyngeus
XII
Right common cardinal vein and right anterior cardinal vein
5th

35. What do membranous interventricular septal defect cause? What does this lead to?
Initial left to right shunting - then switches
Persistent connection between amniotic cavity and spinal canal; low folic acid
Thyroid - cricoid - arytenoids - corniculate cuneiform
...

36. What gene is produced in the zone of polarizing activity?
Endoderm
Sonic Hedgehog
Ectoderm
Primitive atrium

37. What artery is derived branchial (aortic) arch 3?
elevated AFP
VSD
3rd and 4th arches
Common carotid and internal carotid

38. Before birth - blood entering the LA is less than...
2nd; 2nd
blood entering the RA
ACE inhibitors - HCTZ
2; 1

39. From What embryonic layer does the gut tube derivatives arise (lungs liver - pancreas - parathryroid - thyroid follicular cells - thymus)?
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood
Prostaglandins
Midgut; 10th week
Endoderm

40. ______________ is associated with ventral curvature of the penis
Apical ectodermal ridge
Neural crest cells
Mesoderm; epiblast
hypospadias

41. What part of the gut rotates around the SMA? and At what point?
Rhombencephalon
Temporary cervical sinus
Midgut; 10th week
Nutrient and gas for exchange; endometrium

42. From where does the pulmonary arteries and the ductus arteriosus arise?
mesodermal
6th aortic arch
Decreased separation of hemispheres across midline; cyclopia
Week 3-8

43. From where does the medulla form?
Week 3-8
Endoderm
Primitive atrium
Myelencephalon

44. what else is the caudal regression known as? What two teratogen can cause this in the fetus?
Medial palatine processes
VACTERL; OCPs and maternal diabetes
Neural crest cells
Upper 1/3; urogenital sinus

45. When does erythropoeisis begin in the bone marow?
2nd; 2nd
IX; X
28 week onward
Bones - cartilage - and nerves

46. During what week do the limbs begin to form?
Maternally derived; meconium
Week 4
Endoderm
Surface ectoderm

47. What separated myometrium of the uterus from the blastocyst?
3rd; proximal part of the internal carotid artery
Decidual basalis
Dorsal; faulty positioning of genital tubercle
Mesoderm

48. What is the fate of the cervical sinuses that develop from the 2nd -4th branchial grooves?
From teh lung;blood from IVC in RA to LA; fossa ovalis
Obliterated
Neuroectoderm
Temporary cervical sinus

49. What is the Eisenmeger complex?
Lacunae in between the chorionic villi
Ebsteins anomaly; tricuspid atresia
When left to right shunting switching to right to left shunting
During; instrinsic

50. Where does the blastocyst implant in the uterus? During what phase of the menstrual cycle?
Post. sup wall; luteal phase
Increase in oxygen concentration which decreases prostaglandin concentration
Oxygenated; placenta to fetus (IVC)
ACE inhibitors - HCTZ