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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 2?
Medial palatine processes
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric
Day 6; with implantation
Valproate acid

2. By when are the neuropores supposed to fuse?
Tongue
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
4th week
Aortic arch (from left side); right subclavian (on the right)

3. From What embryonic layer do the ependymal cells arise?
Deoxygenated blood; fetal internal iliac arteries to placenta
8
Neuroectoderm
Surface ectoderm

4. Cleft lip is a failure of fusion of ________ and ______.
DiGeorge
Neural crest cells
3rd; proximal part of the internal carotid artery
Maxillary and medial nasal processes

5. From What embryonic layer does the lens of the eye arise?
Neuroectoderm
Surface ectoderm
Telencephalon
Valproate acid

6. What arises from the fourth aortic arch?
8
Aortic arch (from left side); right subclavian (on the right)
Left horn of the sinus venosus
Neuroectoderm

7. From where does the ureteric bud arise? What does it give rise to?
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
All 3
Mesoderm

8. ______________ is associated with ventral curvature of the penis
Mesoderm
hypospadias
Thyroid - cricoid - arytenoids - corniculate cuneiform
Day 6; with implantation

9. The spinal cord is made from...
Right horn of the SV
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast
Decreases
T neuroectoderm

10. What does DHT turn the labioscrotal swelling into? estrogen?
Week 4
Prosencephalon - mesencephalon - rhombencephalon
From teh lung;blood from IVC in RA to LA; fossa ovalis
Scrotum; labia majora

11. What does DHT turn the genital tubercle into? estrogen?
Sperm plus egg
Ventral shaft of penis (penile urethra); labia minora
Arnold chiari; syringomyelia
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs

12. How is amniontic fluid excreted? How is amniotic fluid resorped?
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
Neuroectoderm
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood
Endoderm

13. What are the aspects of fetal alcohol syndrome?
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
After; extrinsic
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
Mental retardation - holoprosencephaly - facial features - fistulas

14. Where is Wnt 7 gene produced?
Apical ectodermal ridge
Physiologic incomplete muscular ventricular septum
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric

15. Which branchial apparatus develops into the thymus?
Branchial arch 2
3rd pouch
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
All or none

16. From What embryonic layer is the bladder and urethra from?
XII
Mesoderm
A vitelline fistula - failure of vitelline duct to close
Synctiotrophoblast; outer; no

17. From What embryonic layer do the parafollicular cells of the thyroid arise?
Annular pancrease
3rd; proximal part of the internal carotid artery
Neural crest cells
Umbilical - midgut herniates through umbilical ring; SMA

18. What congenital abnormality forms a 'double bubble' on xray?
Neural crest cells
Right common cardinal vein and right anterior cardinal vein
Annular pancrease
Week 4; week 3

19. What causes a large posterior fossa in a dandy walker malformation? What is found in this fossa?
Epispadias
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Neuroectoderm
Failure of bony spinal canal to fuse; no; lower vertebral levels

20. What embryological structure gives rise to the trabeculated part of the left and right atrium?
Hepatic circulation; ligamentum venosum
Hemorrhage - bone deformities
Endoderm
Primitive atrium

21. Which branchial derivative accounts for taste in the ant 2/3?
Indomethacin; blocks PG production
blood entering the RA
lumbosacral
Branchial arch 2

22. What is the defect in spina bifida occulta? is there any structural herniation? where on the spinal cord is it usually seen?
Week 2; bilaminar disk; epiblast and hypoblast
IMA
Failure of bony spinal canal to fuse; no; lower vertebral levels
Cerebral hemisphere - thalami

23. By what week is there fetal movement?
Excessive resorption of septum primum or secondum (or both)
Urachus/median umbilical ligament; bladder and yolk sac
Week 4
Week 8

24. What produces testis determining factor? what cells are produced from this? and What do they secrete? does this result in?
...
can make cells
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
Mesoderm

25. Where does fertilization occur?
Cleft lip/palate
Ampulla
Fallopian tube - uterus - upper 1/3 of vagina
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis

26. From what region of the brain does the lateral ventricles and the 3rd ventricle form?
Failure of the urachus to obliterate; outpouching of the bladder
Prosencephalon
Spinothalamic first
Hemorrhage - bone deformities

27. What does the ductus arteriosus shunt blood away from - to where? What is its remnant?
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
IMA
Tetracyclines
Muscular ventricular septum; no

28. What type of radiation is teratogenic ?
Week 10-12; end of 1st trimester
Ionizing
septum primum and/or secundum
Yolk sac; 3rd week

29. What type of blood do umbilical arteries carry? From where to where?
Fetal alcohol syndrome; mental retardation
Stapedius and hyoid artery
Deoxygenated blood; fetal internal iliac arteries to placenta
Endoderm

30. From where is amniotic fluid produced? other than electrolytes and carbs - what else does it contain?
Maternally derived; meconium
Prevent recurrent UTIs
Ectoderm
Ventral ; motor

31. Name two endocardial cushion defects.
Initial left to right shunting - then switches
Ebsteins anomaly; tricuspid atresia
Week 4; week 3
Apical ectodermal ridge

32. What is used to keep the PDA open?
Yolk sac; 3rd week
Endoderm
Prostaglandins
Annular pancrease

33. What trisomy is associated with holoprosencephaly? What teratogen?
V3; VII
Failure of bony spinal canal to fuse; no; lower vertebral levels
Pataus; fetal alcohol syndrome
Lithium

34. Which branchial apparatus develops into the superior parathyroids?
Bulbos Cordis; right ventricle entirely
4th pouch
4th/5th branchial pouches
Hypospadias

35. With the first breath the infant take - pulmonary vasculature resistance _______ which causes an increase in left atrial pressure
3
Before getting pregnant!
arnold chiari associated with thoraclumbar myelomeningocele
Decreases

36. Where does the blastocyst implant in the uterus? During what phase of the menstrual cycle?
Post. sup wall; luteal phase
Mesoderm
Decreased pulmonary resistance in the pulmonary vasculature
Mid gut to yolk sac; omphalomesenteric duct; 7th week

37. What artery is derived branchial (aortic) arch 4?
...
Bulbos Cordis; right ventricle entirely
Aortic arch and prox part of subclavian
Neural crest cells

38. Which branchial derivative creates the middle ear cavity - eustachian tube and mastoid air cells?
Hemorrhage - bone deformities
First branchial pouch
Mesoderm
Obliterated; forms tunica vaginalis

39. From What embryonic layer are the cardiovascular - lymphatics and blood from?
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
Mesoderm
1st branchial arch
Ionizing

40. From What embryonic lare are the odontoblasts from?
Dorsal ventral axis
Mesoderm
Neural crest cells
Failure of bony spinal canal to fuse; no; lower vertebral levels

41. From where does the permanent kidney for? is it most caudal or most cranial?
Dorsal and ventral buds
Outgrowth of mesonephric as ureteric bud; most caudal
Where the epiblast and hypoblast fuse
Stapedius and hyoid artery

42. What is jejunal - ileal - colonic atresia usually due to? What do you see on x ray?
Mesoderm
Deoxygenated blood; fetal internal iliac arteries to placenta
Vascular accident intra uterine; apple peel atresia
VSD

43. What germ layer correlates with the branchial pouches?
Mesoderm; 3 week
Upper 1/3; urogenital sinus
Endoderm
8

44. What artery is derived branchial (aortic) arch 1?
Cytotrophoblast and synctiotrophoblast
Maxillary
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm

45. From What embryonic layer are the schwann cells from ?
3 -4 -6
Prosencephalon - mesencephalon - rhombencephalon
Surface ectoderm
Neural crest cells

46. What artery is derived branchial (aortic) arch 3?
First branchial pouch
Common carotid and internal carotid
Ectoderm
Ebsteins anomaly; tricuspid atresia

47. From where did a branchial cleft cyst arise if it found?
Found in lateral neck; from no obliteration of 2-4th clefts
Right horn of the SV
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
Obliterated

48. What does the mullerian duct develop into? wollffian?
T neuroectoderm
Failure of the urachus to obliterate; outpouching of the bladder
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
Fallopian tube - uterus - upper 1/3 of vagina

49. From what region of the brain does the aqueduct form?
Deoxygenated blood; fetal internal iliac arteries to placenta
Amniotic epithelium
Telencephalon
Rhombencephalon

50. Where is the decidua basalis derived from?
Endometrium
Week 3-8
Neuroectoderm
Dorsal ventral axis